Proceedings of the 63rd Gulf and Caribbean Fisheries Institute November 1 - 5, 2010 San Juan, Puerto Rico

Sponge Mortality at Marathon and Long Key, Florida: 

Patterns of Species Response and Population Recovery

JOHN M. STEVELY1*, DONALD E. SWEAT2, THERESA M. BERT3, 

CARINA SIM-SMITH4, and MICHELLE KELLY4

1Florida Sea Grant College Program, Marine Extension Program, 1303 Seventeenth Street West, Palmetto, Florida 34221 

USA. *jsmarine@ufl.edu. 

2Florida Sea Grant College Program, Marine Extension Program, 830 First Street South, St. 

Petersburg, Florida 33701 USA. 

3Florida Fish and Wildlife Conservation Commission, Fish and Wildlife Research 

Institute, 100 Eighth Avenue Southeast, St. Petersburg, Florida 33701 USA. 

4National Centre for Aquatic Biodiversity and 

Biosecurity, National Institute of Water and Atmospheric Research Limited, Private Bag 109 695, New Market, Auckland, 

New Zealand.

ABSTRACT

In the early 1990s, widespread sponge mortality events occurred in the Florida Keys, USA. These mortality events were 

coincidental with successive blooms of the picoplanktonic cyanobacterium Synechococcus sp. Although the specific cause of 

sponge death remains unknown, we conclude that bloom conditions caused the death of these sponges. We documented the effects

of the mortality events on sponge community biomass and followed the sponge population response of 23 species for up to 15 years

(1991 - 2006). In doing so, we provide an unprecedented, long-term, and detailed view of sponge population dynamics in the 

Florida Keys, following a set of environmental conditions that caused widespread mortality. Abundance of many sponge species

following the mortality events was dynamic and contrasts with work done on deep-water sponge communities that have shown such 

communities to be stable over long periods of time. Recovery of the sponge community biomass in the Florida Keys was slow, 

taking 10 - 15 years. Some species showed consistent long-term trends but many others displayed constantly changing abundance in 

time and space. We conclude that sponge deaths resulting from relatively infrequent bloom conditions can chronically reduce 

sponge community biomass and have potentially long-term and widespread ecological consequences. Hurricane Wilma directly hit 

the study area in 2005, allowing us to also document the effects of a hurricane on sponge populations. Although this hurricane event 

significantly impacted sponge abundance, in general, massive, long-lived sponges that dominate sponge community biomass in the 

area tended to be more resistant. Hence, we conclude that sponge community biomass will recover more quickly than following 

bloom-related mortality events.

KEY WORDS: Algae bloom, cyanobacteria, hurricanes, mortality, Porifera, sponges, sponge population dynamics

La Mortalidad de las Esponjas en los Cayos Marathon y Long de la Florida, Estados Unidos: 

Patrones de la Respuesta de las Especies y de la Recuperación de la Población

En el comienzo de los 1990s, la mortalidad de las esponjas se propago extensamente en los cayos de la Florida, Estados 

Unidos. Estos eventos de mortalidad coincidieron con la proliferación de cyanobacteria picoplanctonica Synechococcus sp. A pesar 

de que la causa especifica de muerte de las esponjas continua siendo desconocida, concluimos que las condiciones de esta 

proliferación causaron la muerte de dichas esponjas. Fuimos capaces de documentar los efectos de estos eventos de mortalidad en la 

biomasa de la comunidad de esponjas y seguir la respuesta de la población de esponjas de 23 especies por hasta quince años (1991-

2006). Al hacer esto, proveemos una vista sin precedentes, detallada, y a larga escala de la dinámica de la población de las esponjas 

en los cayos de la Florida, después de una serie de condiciones medioambientales que propago mortalidad. Abundancia de varias 

especies de esponjas siguiendo eventos de mortalidad fue dinámica y contrasta con el trabajo realizado en comunidades de esponjas 

de agua profunda que demuestran que tales comunidades son estables a lo largo de extensos periodos de tiempo. La recuperación de 

la biomasa de comunidades de esponjas en los cayos de la Florida fue lenta y tomo al menos quince años. Algunas especies 

demostraron tendencias consistentes a lo largo de periodos extensos de tiempo pero muchas otras demostraron una abundancia de

cambios en tiempo y espacio. Concluimos que la muerte de esponjas resultando de una proliferación relativamente inconsistente 

puede crónicamente reducir biomasa de comunidades de esponjas y tener consecuencias ecológicas potencialmente extensas. En el 

2005 el huracán Wilma afecto el área de estudio directamente, dejándonos documentar los efectos de un huracán en la población de

esponjas. Aunque este huracán impacto severamente la abundancia de esponjas, en general, las esponjas más grandes y mayores que

dominaban el área de la biomasa de la comunidad de esponjas perduraban más. Por lo tanto, concluimos que la biomasa de la 

comunidad de esponjas se recuperara más rápido en comparación a los eventos de mortalidad relacionados con las proliferaciones.

PALABRAS CLAVE: Proliferación de algas, cyanobacteria, huracanes, mortalidad, Porifera, esponjas, dinámicas de la población 

de esponjas

La Mortalité Éponge dans les Florida Keys, Etats-Unis: 

Les Modes de Rétablissement des Populations d'Espèces 

MOTS CLÉS: Mortalié éponge, Porifera, modes de rétablissement
Stevely, J.M. et al. GCFI:63 (2011) Page 385

INTRODUCTION

In the early 1990s, sponge populations within hundreds of square kilometers of the shallow lagoonal waters 

(< 3 m deep) north of the middle and upper Florida Keys 

were decimated (Figure 1). Circumstantial evidence 

implies that it was blooms of the picoplanktonic cyanobacterium Synechococcus sp. that caused widespread sponge 

mortality because sponge mortality events were coincidental with Synechococcus blooms that occurred sporadically between November 1991 and 1995 (Butler et al. 

1995, Stevely and Sweat 1995). Two major bloom events 

occurred. The initial bloom extended from mid-November 

1991 until February 1992, when cyanobacteria cell 

densities reached 109cells/L, compared with less than 104

cells/L outside the bloom (Butler, et al. 1995). Butler et al.

(1995) reported that over 80% of several sponge species 

and more than 40% of the loggerhead sponges 

(Spheciospongia vesparium) at one study site were killed. 

They documented that, later, a total of 71% of sponges 

located near the center of the bloom were dead, whereas 

only 5% were damaged near the periphery of the bloom. 

The second, larger, more persistent bloom occurred from 

October 1992 until May 1993. This bloom developed in 

north central Florida Bay but its subsequent position was 

dynamic and at times extended south along the Florida 

Keys. Additional sponge deaths were reported at locations 

that were exposed to bloom waters (Butler et al. 1995). 

Cyanobacteria blooms were observed again in 1994 and 

1995. These blooms affected the Long Key area to some 

degree. By this time, there were no sponges left at Butler’s 

et al.’s (1995) experimental sites. In 1996 and 1997, 

repeated algal blooms again occurred in the central portion 

of Florida Bay (Phlips et al. 1999). These may have had 

some lesser effects at Long Key. 

Sponges are a major component of benthic communities in many hard bottom coastal environments, are a 

particularly dominant structural feature in shallow lagoon 

hard bottom environments in the Florida Keys (Chiappone 

and Sullivan 1994, Field and Butler 1994), and are of 

ecological and economic significance. The affected 

Florida Keys area is recognized for its importance as a 

marine nursery (Holmquist et al. 1989, Thayer and Chester 

1989), particularly for spiny lobster (Panulirus argus 

Latreille 1804) (Field and Butler 1994, Herrnkind and 

Butler 1994). Post-larval spiny lobsters often seek shelter 

under loggerhead sponges (Herrnkind and Butler 1994). 

The area also supports a significant commercial bath 

sponge fishery.

Although sponges frequently dominate the faunal 

assemblages inhabiting hard substratum habitats in 

tropical, temperate, and polar regions, they are rarely a 

major component of long-term benthic monitoring 

programs because accurate biodiversity estimates are 

difficult to obtain (Bell et al. 2006, Carbollo et al. 2008). 

Just prior to the first sponge mortality event, Stevely et al.

(2010) completed an inventory of the sponge community 

abundance and biomass in the bloom-affected area, 

providing the base-line data for the present study. 

In response to the widespread sponge deaths subsequent to Stevely et al.’s (2010) sponge community survey, 

we extended the study to monitor the recovery of populations of specific species until 2006. After the 2005 survey 

work was completed, Hurricane Wilma brought hurricaneforce winds throughout the study area. The co-occurrence 

of Hurricane Wilma in the study area allowed us to also 

provide insight into how hurricanes affect sponge population dynamics in our study area. Thus, here we provide a 

unique, long-term, detailed view of sponge population 

dynamics following a set of environmental and meteorological conditions that have caused widespread mortality in 

the Florida Keys.

Figure 1. Location of study sites, spatial extent of cyanobacteria blooms (adapted from Butler et al. 1995), and track 

of hurricane Wilma. Water mass A represents the approximate boundaries of the November 1991 to January 1992 

bloom. Water mass B represents the October 1992 to May 

1993 bloom. The boundaries of each bloom are approximate because the boundaries were dynamic and continually 

changing. The extents of maximum sustained winds of 

Wilma at 1030 UTC October 24, 2005 (contour lines) are 

from the U.S. National Oceanographic and Atmospheric 

Administration Hurricane Research Division.

METHODOLOGY

Field Methods

Stevely et al. (2010) surveyed 15 sites throughout an 

area north of the middle and upper Florida Keys and 

collected data on diversity (number of species), abundance 

(number of individuals in each species), and volumetric 

biomass of the majority of sponge species in the communities represented. Two sites on the Gulf of Mexico side of 

the Florida Keys--offshore from Marathon (Vaca Key) and 

from Long Key--were chosen for subsequent monitoring, 

which commenced in 1993 (Figure 1). These two sites 

represent the greatest degree of geographic separation of 

the original 15 sites, and Marathon is the most distant site 
Page 386 63rd Gulf and Caribbean Fisheries Institute 

from the bloom epicenter 

Initially, stations at the two sites (Table 1) were 

determined using LORAN C; but after 1993, the Differential Global Positioning System (DGPS) was used. 

Latitude/longitude coordinates of stations initially determined using LORAN C were re-recorded using DGPS. 

This conversion was necessary because of potential 

discrepancy between the two navigational systems in 

determining latitude and longitude. Permanent reference 

marker stakes and lines were established at each station in 

1995 to verify that we were indeed sampling the same 

sites.

The typical shallow lagoonal habitat at Marathon and 

Long Key consists of low-relief limestone bedrock overlain 

with a thin veneer of sediment, interspersed with seagrass 

meadows growing in deeper sand. This habitat is generally 

populated by a complex assemblage of sponges, octocorals, 

corals, and macroalgae, including calcareous Halimeda

spp. and Penicillus spp. and red drift algae such as 

Laurencia spp. The methodology we designed for 

monitoring sponge abundance at the two sites was the same 

as that used for the other 13 sites surveyed by Stevely et al. 

(2010). Briefly, at each site, sponge abundance was 

determined by counting all sponges within twelve 100-m 

by 2-m transects (200 m2). Four transects per dive were 

conducted and three dives were conducted at each site, so 

that the total area covered was 2400 m2. On one occasion, 

at Long Key in 1991, equipment failure prevented the 

completion of the full complement of 12 transects. 

Other than in 1992 and 1996, surveys were conducted 

annually from 1991 to 2006, during a two-week interval 

sometime between June and August. Bloom conditions 

caused low visibility and prevented work in 1992 and 

logistical constraints prevented work in 1996. Following 

the widespread mortality of sponges after the 1991 survey, 

our initial objectives--to document commercial bath sponge 

and total sponge community biomass (Stevely et al. 2010)-

-were refocused to collect more detailed data on as many 

species as possible. Hence, we added additional species 

counts in 1994, 1995, and 1997, as funding allowed. 

Consequently, we present data on abundance trends of 

many species for which we do not have baseline premortality data; but based on our personal observations, 

most, if not all, were present prior to the mortality. In 

addition, three sponges--Amphimedon viridis, Petrosia 

(Petrosia) cf. pellasarca, and Xestospongia subtriangularis, rare or absent at Marathon between 1991 and 1998, 

were added later (A. viridis in 2002; P. (P.) cf. pellasarca 

and X. subtriangularis in 2005).

The extremely variable shape of many sponge species 

precluded the use of linear measurements to reliably 

determine sponge dimensions and hence volume. Sponge 

volume was thus determined by measuring the volume of 

water displaced by an individual, as described in Stevely et 

al. (2010). Sponge volumetric biomass was determined in 

1991, before the sponge mortality event, and in 1993, after 

the event, allowing us to document both numerical and 

biomass declines resulting from the mortalities.

The seven sponge species we surveyed in 1991 prior to 

the mortality were chosen because of their conspicuous 

size and/or economic importance. The 13 species added to 

the surveys between 1994 and 1997 were included to 

develop a more comprehensive understanding of sponge 

community response following the Synechococcus blooms. 

The three sponges added in 2002 or 2005 were included 

because of their notable and sudden increase in abundance.

These additional species were chosen because they could 

be easily identified in the field after initial identification in 

the laboratory and they, too, were conspicuous in size, or 

were important to the local economy. All species are listed 

in Table 2.

Statistical Analysis 

To determine if changes in abundance for each species 

were significant, statistical analyses were conducted using 

the software statistical package SigmaStat (version 2.0 for 

Windows 95, Jandel Corporation). Each data set was 

tested for normal distribution and equality of variance. If 

both these conditions were met, a T-Test was used to test 

for a difference between two means and a One Way 

Analysis of Variance (ANOVA) was used to test for 

differences among three or more means. When the data set 

failed the test for either normality of distribution or 

equality of variance, a Mann-Whitney Rank Sum test was 

used to test for differences between two medians and a 

Kruskal-Wallis Analysis of Variance on Ranks was used to 

test for differences among three or more medians. When 

samples sizes were equal, Tukey’s Test and the less 

conservative Student-Newman-Kuels test were used to 

locate the significant differences among means. When 

sample sizes were unequal, Dunn’s All Pairwise Multiple 

Comparison procedure was used. Unless otherwise noted, 

the results of the Tukey’s Test are presented.

RESULTS

In our previous study (Stevely et al. 2010), more than 

24,000 sponges were recorded from over 3.3 ha of area 

surveyed. Mean abundance over the 15 sites was 7,200 

sponges/hectare (range: 3,171 - 15,200), and the mean 

biomass for the entire area was 364 ml/m2(range: 200 –

Table 1. Latitude and longitude of Long Key and 

Marathon sampling stations in the Florida Keys. Site 

locations are shown in Figure 1.

Site/station Latitude Longitude Depth (m)

Marathon

Dive 1 24o46.485 81o03.789 2.7

Dive 2 24o46.465 81o03.751 2.7

Dive 3 24o46.474 81o03.742 2.7

Long Key

Dive 1 24o51.230 80o48.805 2.5

Dive 2 24o51.241 80o48.791 2.5

Dive 3 24o51.211 80o48.820 2.5
Stevely, J.M. et al. GCFI:63 (2011) Page 387

700). The sponge community biomass in the area included 

in that study was dominated by two large sponge species:

S. vesparium and Ircinia campana (vase sponge). 

Two years later, as documented herein, sponge 

abundance at Marathon and Long Key had declined by 

69% and 45%, respectively (Figure 2A). Sponge biomass 

at Marathon and Long Key had declined remarkably, by 

93% and 88%, respectively (Figure 2B). With few 

exceptions, all of the largest sponges were completely 

decimated. Together, S. vesparium and I. campana 

accounted for 68% of the total sponge community biomass 

loss between 1991 and 1993.

Throughout the present study, total numerical sponge 

abundance was greater at Marathon than at Long Key 

(Figure 3). Total abundance at Marathon significantly (p < 

0.05) decreased between 1991 and 1993. Recovery was 

Table 2. Sponge species monitored at Marathon and Long Key

Order Family Species

SPIROPHORIDA Bergquist & Hogg, 

1969

Tetillidae Sollas, 1886 Cinachyrella alloclada (Uliczka, 1929)3

HADROMERIDA Topsent, 1894 Clionaidae d’Orbigny, 1851 Spheciospongia vesparium (Lamarck, 1815)1

Cliona varians (Duchassaing and Michelet, 1864)1, 2

Tethyidae Gray, 1848 Tectitethya crypta (de Laubenfels, 1949)3

HALICHONDRIDA Vosmaer, 1887 Halichondriidae Gray, 1867 Halichondria (Halichondria) melanodocia de Laubenfels, 

19363

HAPLOSCLERIDA Topsent, 1928 Chalinidae Gray, 1867 Adocia implexiformis (Hechtel, 19653

Chalinula molitba (de Laubenfels, 1949)3

Callyspongiidae de Laubenfels, 1936 Callyspongia (Cladochalina) vaginalis (Lamarck, 1814)3

Niphatidae van Soest, 1980 Amphimedon viridis Duchassaing & Michelotti, 18644

Niphates erecta Duchassaing & Michelotti, 18643

Petrosiidae van Soest, 1980 Xestospongia subtriangularis (Duchassaing, 1850)4

Petrosia (Petrosia) cf pellasarca (de Laubenfels, 1934)4

POECILOSCLERIDA Topsent, 1928 Tedaniidae Ridley & Dendy, 1886 Tedania (Tedania) ignis (Duchassaing & Michelotti, 

1864)3

Coelosphaeridae Dendy, 1922 Lissodendoryx isodictyalis (Carter, 1882)3

DICTYOCERATIDA Minchin, 1900 Spongiidae Gray, 1867 Spongia (Spongia) barbara Duchassaing & Michelotti, 

18641

Spongia barbara dura Hyatt, 18771

Spongia (Spongia) graminea Hyatt, 18771

Hippospongia lachne de Laubenfels, 19361

Irciniidae Gray, 1867 Ircinia campana (Lamarck, 1814)1

Ircinia strobilina (Lamarck, 1816)1

Ircinia felix (Duchassaing & Michelotti, 1864)1

Thorectidae Bergquist, 1978 Hyrtios proteus Duchassaing & Michelotti, 18643

VERONGIDA Bergquist, 1978 Aplysinidae Carter, 1875 Aplysina fulva (Pallas, 1766)3

slow; and it was not until 2001 that abundance had 

increased to the point that it was statistically indistinguishable from the 1991 abundance. Sponge abundance at

Marathon peaked in 2004; but then significantly (p < 0.05) 

declined in 2006, following the 2005 hurricane season. 

The pattern of sponge mortality and recovery at Long 

Key was different and less pronounced than the pattern 

observed at Marathon. Significant declines for several 

important species, in terms of their contribution to sponge 

community biomass, were observed. However, overall 

abundance in 1993 and 1994 did not differ significantly 

from the 1991 pre-mortality abundance, nor did the 

hurricanes greatly affect overall abundance. Evidently, the 

effects of the bloom-induced mortalities where less at 

Long Key, even though it was closer to the bloom 

epicenter.

1 Monitoring initiated during or prior to 1991. 

2 Despite the absence of 1991 and 1993 abundance data for Cliona varians, and 1991 abundance data for Spongia barbara 

dura, field observations confirmed their presence at Marathon and Long Key in relatively high numbers, and their subsequent decimation in 1993.

3 Monitoring initiated between 1994 and 1997. 

4

- Monitoring initiated 2002 or 2005.
Page 388 63rd Gulf and Caribbean Fisheries Institute 

Patterns of Sponge Population Response to Environmental Perturbation

Five clear patterns of change in abundance were 

apparent over the study period (Table 3): 

i) Rapid decline in 1993 followed by gradual 

recovery; 

ii) Fluctuating abundance; 

iii) Gradual decline; 

iv) Low abundance, no change; and 

v) Abrupt increase in abundance after Hurricane 

Wilma. 

The individual pattern of response for each species 

surveyed is described below. The statistical significances 

of the observed changes in abundance are summarized in 

Table 3. 

Figure 2. Effects of sponge mortality on abundance (A) 

and biomass (B) at Marathon and Long Key (±S.E. bars).

Figure 3. Total sponge abundance at Marathon and Long 

Key, 1991–2006 (average number/transect ± S. E. bars). 

The shaded area depicts timing of 1991–1993 bloom 

events at both sites. Large arrows represent timing of 

bloom events in 1994 and 1995 in the vicinity of Long Key. 

Smaller arrows represent timing of blooms in Florida Bay 

that might have affected Long Key area. The star represents the timing of Hurricane Wilma. 

Table 3. General patterns of response of sponge species 

at Marathon and Long Key. SNK: P < 0.05; Tukey’s: P < 

0.05; Dunn’s: P < 0.05; T-Test: P < 0.05. ns; not significant. Dash: not present in transects at this study site.

General patterns of response

Marathon Long Key

Rapid decline in 1993 with recovery to 1991 levels

Spheciospongia vesparium SNK, Tukey’s Dunn’s

Cliona varians SNK, Tukey’s SNK, Tukey’s

Ircinia campana SNK, Tukey’s Dunn's

Ircinia felix SNK, Tukey’s SNK, Tukey’s

Ircinia strobilina Tukey’s SNK, Tukey’s

Hippospongia lachne SNK1ns2

Spongia (Spongia.) ― ns2

Spongia barbara dura SNK, Tukey’s SNK, Tukey’s

Spongia (Spongia) SNK, Tukey’s ―

Fluctuating abundance

Cinachyrella alloclada SNK, Tukey’s SNK, Tukey’s

Halichondria 

(Halichondria) mela- SNK, Tukey’s SNK, Tukey’s

Adocia implexiformis SNK, Tukey’s ns

Lissodendoryx isodictyalis SNK, Tukey’s SNK, Tukey’s

Chalinula molitba SNK, Tukey’s Dunn’s

Niphates erecta SNK, Tukey’s SNK, Tukey’s

Hyrtios proteus SNK, Tukey’s ns

Amphimedon viridis ns2 ―

Petrosia (Petrosia) cf 

pellasarca T- test ―

Gradual decline

Hyrtios proteus ns SNK, Tukey’s

Adocia implexiformis ― SNK, Tukey’s

Tedania ignis ns SNK, Tukey’s

Low abundance, no change

Tectitethya crypta ns3ns3

Tedania ignis ns3 ―

Callyspongia vaginalis ns2 ―

Abrupt increase after Hurricane Wilma in 2005

Aplysina fulva SNK, Tukey’s SNK, Tukey’s

Xestospongia subtrian- T-test ―

1 Non-significant under Tukey’s test.

2 Kruskal-Wallis test indicated a highly significant difference in the medians but SNK, Tukey’s, or Dunn’s 

could not differentiate between the means.

3 Kruskal-Wallis test did not detect a significant difference among medians.
Stevely, J.M. et al. GCFI:63 (2011) Page 389

Spheciospongia vesparium — The loggerhead sponge 

(Figure 4A, Table 3) is a massive purple to brownish-black, 

hemispherical sponge that is extremely common in shallow 

lagoonal hard-bottom communities in and around the 

Florida Keys (Donahue 2008) and the greater Caribbean 

region (Wiedenmayer 1977). The aquiferous system of this 

species provides habitat for a myriad of invertebrates 

(Pearse 1950; Erdman and Blake 1987), including juvenile 

spiny lobsters. In 1991, Stevely et al. (2010) found S. 

vesparium to be the most important component of the 

sponge community in terms of biomass (58%). 

In 1993, S. vesparium was eliminated from the 

Marathon site. Recovery was slow until 2000, when 

significant (p < 0.05) recruitment was recorded at Marathon. By 2001, population abundance had statistically 

recovered to pre-1991 levels. However, the mean diameter 

of the sponges in 2003 was only 12 cm (range: 4 cm – 23 

cm), significantly (T-Test, p < 0.001) less than the mean 

diameter of 27 cm (range: 9 cm – 42 cm) in 1991. Thus, 

although abundance had recovered by 2003, the biomass 

still had not recovered, confirming that this species is 

relatively long-lived and slow growing.

Recovery of S. vesparium at Long Key was slower and 

less pronounced than at Marathon. The principal mode of 

recovery may have differed between the two study areas. 

In 1993, the population of S. vesparium at Long Key was 

decimated but not eliminated; two large, irregularly shaped 

specimens were found within the survey transects area, and 

several specimens were observed outside the survey 

transects. [Butler et al. (1995) also observed that localized 

necrosis in S. vesparium resulted in irregularly shaped 

specimens.] Recovery was very slow and it was not until 

13 years later, in 2006, that the mean abundance was 

significantly (Dunn’s method, p < 0.05) greater than mean 

abundance in 1993; but it was still less than that of 1991. 

Field observations at Long Key suggest that recruitment in 

the years 1993 through 1999 was via asexual regeneration 

of remaining specimens, rather than new recruitment via 

sexual reproduction and larval dispersion. Spheciospongia 

vesparium can bore into calcareous material, creating 

chambers and canals (Wiedenmayer 1977) that act as 

refugia during adverse conditions (Kelly 1986, KellyBorges and Bergquist 1988). In 2000, Long Key individuals were, on average, significantly (p < 0.001) larger (mean 

diameter 21.4 cm) than those at Marathon (mean diameter 

10.0 cm), suggesting that they had grown from remnant 

individuals rather than from larvae recruited over time. 

In general, S. vesparium had greater resistance to the 

algal blooms than most sponge species. At some locations, 

S. vesparium did not decline after the bloom events, 

whereas other species such as I. campana were eliminated 

(J. Stevely Unpbl. data). One location was less than 2 km 

from the Long Key survey site. 

Cliona varians — The brown variable sponge previously 

known as Anthosigmella varians (Figure 4B, Table 3), is 

common throughout Florida and the general Caribbean 

region. It has a tough consistency that allows it to prevail 

in shallow habitats with coarse sediment and strong wave 

action (Rützler 2004). It occurs as very large encrustations 

in high-energy environments and as a smaller massive 

form that may be digitate or globular in lower-energy 

environments (Wiedenmayer 1977, Vincente 1978). Like 

S. vesparium, this species also bores basally into calcareous substrate. It is considered to be an aggressive competitor for substrate (Vincente 1978). Cliona varians significantly (p < 0.05) increased in abundance throughout the 

study at both sites from 1994, when its abundance was first 

recorded.

Ircinia campana — (Figure 4C, Table 3) is common in the 

Florida Keys and is typically a large and easily recognizable, yellowish-brown sponge with a distinctive vase-shaped 

morphology. It was eliminated at both Marathon and Long 

Key in 1993. There was no evidence of recruitment at 

Marathon or Long Key until 2002 and 2003, respectively. 

Abundance had significantly (p < 0.05) increased at 

Marathon by 2005, but abundance at both sites remained 

far below levels found in 1991. Mean diameter in 2004 

(12.5 cm) was still significantly (p < 0.05) smaller than the 

mean size found in the study area in 1991 (18.2 cm).

Ircinia felix — The branching stinker sponge (Figure 4D, 

Table 3) is a massive, lobate sponge that is typically 

yellowish-brown with darker oscular linings. In the lowenergy environments of the Gulf of Mexico side of the 

middle to upper Florida Keys, this sponge branches 

extensively to form a mat. Ircinia felix was eliminated at 

both Marathon and Long Key by 1993, but recovered 

quickly and significantly (P < 0.05) to 1991 levels at both 

sites. As with the other sponges previously described, 

recruitment at Long Key lagged behind that at Marathon. 

Ircinia strobilina — The stinker sponge (Figure 4E, Table 

3) is a massive, spherical sponge common throughout the 

Florida Keys and general Caribbean region. Ircinia 

strobilina was decimated in 1993 at both Marathon and 

Long Key. Although not very abundant in 1991, recruitment at Marathon was rapid and pronounced; abundance 

eventually exceeded 1991 levels by almost 7 times. In 

contrast, at Long Key, recruitment was limited; abundance 

in 2006 was still significantly (p < 0.05) lower than in 

1991. 

Hippospongia lachne — is known locally as the 

sheepswool or wool sponge (Figure 4F, Table 3). The 

softness and durability of the fiber skeleton, when prepared 

as a bath sponge, makes it by far the most valuable 

Caribbean commercial bath sponge (Storr 1964). Hippospongia lachne was eliminated at both sites by 1993. 
Page 390 63rd Gulf and Caribbean Fisheries Institute 

Recovery of the population was limited; the first appearance of specimens occurred in 1998 and 2002 at Marathon 

and Long Key, respectively. Due to low abundance and 

limited recovery, statistical confirmation of recovery was 

not clearly established (Table 3). We know, however, that 

wool sponges were being harvested at Channel Key Bank 

and other locations that had been decimated, thus indicating successful recovery at some locations. Recovery of H. 

lachne to 1991 levels at these other sites was verified by 

further survey work (J. Stevely Unpbl. data). 

Spongia (S.) barbara — The yellow sponge (Figure 4G, 

Table 3), another commercially important bath sponge in 

the Caribbean region, is characterized by a symmetrical 

columnar shape and smooth surface. Spongia (S.) barbara 

was not present at Marathon, but was found at Long Key in 

1991 at an abundance that could support commercial 

harvest. It was eliminated from Long Key by 1993. By 

1997, recruitment was evident, and between 1999 and 2006 

abundance was comparable to that of 1991. 

Spongia barbara dura — (Figure 4H, Table 3) It is 

important to note here that differentiation of Spongia

species can be difficult in the field (Cook and Berquest 

2002) and there is confusion regarding the proper taxonomic status of this sponge (Van Soest 1978). However, 

we were to able to differentiate it from other Spongia

(Stevely et al. 2010). There are no recorded landings of the 

commercial bath sponge S. barbara dura (hardhead 

sponge) in Florida, because the sponge rarely reaches the 

minimum legal size in these waters. However, it is 

occasionally harvested in the Bahamas (J. Stevely Pers. 

observation). Abundance data for S. barbara dura was not 

collected at Marathon or Long Key in 1991 because it was 

not considered to be a commercially valuable species 

(Stevely et al. 2010). Following the mortality events, S.

barbara dura exhibited rapid recruitment with significant 

(p < 0.05) increase in abundance at both areas. Although 

the pattern of recruitment at Long Key was very similar to 

that at Marathon, overall abundance was consistently 

lower. 

Spongia (S.) graminea — The glove sponge (Figure 4I, 

Table 3) is characterized by its massive columnar to subconical shape with distinctive ridges on the sides. Although S. (S.) graminea is a commercial bath sponge, it is 

considered to be of inferior quality because of its weak 

spongin fiber skeleton; and it is infrequently harvested in 

Florida. Spongia (S.) graminea was only present in the 

Marathon and was eliminated by 1993. Between 1995 and 

2006 the population gradually recovered, but abundance in 

2006 was still lower than abundance in 1991. Both the 

decline and the recovery were significant (p < 0.05).

Figure 4. Sponge species exhibiting rapid decline 

followed by consistent, statistically significant recovery 

(average number/transect ± S.E. bars). The shaded area 

(shown on Figures 4A and 4F) depicts timing of 1991 –

1993 bloom events at both sites; large arrows represent 

timing of bloom events in 1994 and 1995 in the vicinity of 

Long Key and smaller arrows represent timing of blooms in 

Florida Bay that might have affected Long Key area. The 

star represents the timing of Hurricane Wilma. 
Stevely, J.M. et al. GCFI:63 (2011) Page 391

Cinachyrella alloclada — Orange ball sponge (Figure 5A, 

Table 3) is a relatively small globular bright orange or 

yellow sponge, usually covered with sediment. It is 

characterized by the presence of sunken incurrent 

porefields (porocalices) and a hairy surface, and is very 

common in the study area. This sponge exhibited significant (p < 0.05) fluctuations in abundance at both Marathon 

and Long Key over the duration of the study. 

Cinachyrella alloclada appears to have been relatively 

resistant to the plankton blooms at both sites; in 1994, it 

had the highest recorded abundance of all species surveyed, and field observations indicated it was also 

abundant in 1993 prior to its inclusion in this survey. It 

remained abundant at Long Key throughout 1994 - 1995, a 

time when it was likely to have been exposed to bloom 

waters. However, because we do not have pre-bloom 

abundance records for C. alloclada, strong recruitment in 

1993 rather than resistance to the bloom cannot be ruled 

out. Nevertheless, this species was reported by Peterson et 

al. (2006) to be a major contributor to sponge community 

biomass in areas of Florida Bay that were repeatedly 

exposed to bloom water. Butler (2008) reported that C.

alloclada was the most resistant sponge during a more 

recent bloom event. The extremely hirsute surface of this 

species may aid in deterring the incurrent flow of Synecococcus by trapping a layer of sediment, which acts as an 

additional filtration barrier. 

Halichondria (H.) melanodocia — (Figure 5B, Table 3) is 

a small amorphous sponge that is black with greenish 

yellow tinges. The sponge is soft and easily torn. This 

species rapidly increased in abundance at Long Key around 

1995 but declined significantly (p < 0.05) over the next 5 

years. In contrast, abundance at Marathon did not change 

significantly until 2001, when it increased two-fold; after 

which it declined as well. This “boom and bust" pattern is 

characteristic of an opportunistic recruitment strategy. 

Adocia implexiformis — (Figure 5C and 6B, Table 3) 

forms a lavender tubular mass that easily fragments, and is 

typically found growing attached to hard substrate and 

unattached among seagrasses. The species exhibited 

significant (p < 0.05) fluctuations in abundance, exploding 

to an almost 20 - fold peak at Marathon in 2000. The 

observed changes in abundance at Marathon were among 

the most dramatic observed for any species during this 

study. At Long Key, levels of abundance were quite low 

compared with those at Marathon, and abundance significantly (p < 0.05) decreased over the course of the study. 

Following the 2005 hurricane season, A. implexiformis was 

mostly absent from both areas.

Lissodendoryx isodictyalis — (Figure 5D, Table 3) is 

typically subspherical, and is characterized by dull yellow 

coloration and a translucent diaphanous surface. This 

sponge is frequently loosely attached to sediment in areas 

with a thin veneer of sediment, but may also occur in 

seagrass areas. At Marathon, L. isodictyalis abundance 

increased significantly and then significantly declined (p < 

0.05 for both). At Long Key, this species was uncommon, 

and changes were not significant.

Chalinula molitba — (Figure 5E, Table 3) is a small, soft, 

fragile sponge with a distinctive pale blue to violet 

coloration. Although typically encrusting with lobes, it 

was stringy at our study sites. Abundance significantly 

increased and decreased at both Marathon and Long Key 

over the course of the study (p < 0.05 for all). The most 

notable change in abundance was a sharp decline at Long 

Key between 1995 and 1997. In general, changes in 

abundance at Long Key were more pronounced than were 

changes at Marathon. 

Niphates erecta — The lavender rope sponge (Figure 5F, 

Table 3) is relatively common and easily recognized by its 

dull gray, solid, single, ramose branches. It was relatively 

abundant at both Marathon and Long Key immediately 

after the bloom events. Patterns of abundance were 

similar at both Marathon and Long Key. In general, N. 

erecta exhibited significant (p < 0.05) increases and 

decreases in abundance at both study areas over the course 

of the study.

Hyrtios proteus — (Figure 5G and 6A, Table 3) is a small 

amorphous purplish-black sponge with a distinctive 

conulose surface; and it is softly resilient. This sponge 

was much more abundant at Marathon than at Long Key. 

In general, this species significantly (p < 0.05) declined at 

both areas. However, at Marathon, a significant (p < 

0.05) spike in abundance occurred before further decline 

(Figure 5G); whereas, at Long Key, abundance declined 

to near zero and never increased (Figure 6A). By the end 

of the study, H. proteus was uncommon at both areas.

Amphimedon viridis — (Figure 5H, Table 3) is easily 

recognized by its brilliant green coloration and branching 

habit. Although our abundance data for this species is 

limited, the data were sufficient to document that A. 

viridis had indeed recruited into the Marathon area to a 

significant degree. It was not found at Long Key.

Petrosia (Petrosia) cf. pellasarca — (Figure 5I, Table 3) 

This sponge species is very irregularly shaped and has a 

characteristic chocolate brown coloration. It is considered 

to be a species of Petrosia (K. Rützler, National Museum 

of Natural History, Pers. communication), and is similar 

to the sponge recognized as Petrosia (P.) pellasarca (de 

Laubenfels 1934) in the Caribbean today (Zea 1987). We 

began to collect abundance data for this species because it 

had essentially been absent for many years and was 

obviously a new and common recruit, at least in 2005. 

Abundance significantly (p < 0.05) decreased following 

the hurricanes. 
Page 392 63rd Gulf and Caribbean Fisheries Institute 

Tedania (T.) ignis — The fire sponge (Figure 6C, Table 3) 

is widespread throughout the Caribbean and is characterized by its bright red coloration and irritation to the skin 

upon handling. This species was never common at 

Marathon during the study, and showed no significant 

trends. It was more abundant at Long Key, but it underwent a long-term gradual and significant (p < 0.05) 

decline.

Aplysina fulva — The scattered-pore rope sponge (Figure 

7A, Table 3) is easily recognized by its morphology (long 

thin elastic branches), texture (rubbery, smooth), and color 

(yellowish-brown with lavender tinges). Initially, it was 

relatively uncommon at both sites. However, abundance 

increased steadily and significantly (p < 0.05) at Marathon 

to the point that it was ranked the fifth-most abundant 

species in 2006. A similar but less pronounced pattern 

was observed at Long Key.

Xestospongia subtriangularis — The sprawling sponge 

(Figure 7B, Table 3) is a large caramel-colored branching 

sponge, with a brittle texture. The limited data for this 

species documents that it was another species that 

recruited into the Marathon area long after the sponge 

mortality. Interestingly, it significantly (p < 0.05) 

increased in abundance after the hurricanes. 

Tectitethya crypta — is a hemispherical to conical sponge, 

typically covered with a thin layer of sediment (Table 3). 

It is recognizable by the is black with a greenish tinge. 

This species was relatively common at Long Key but less 

so at Marathon, and in both locations it was noticeably 

clumped in distribution. No significant change in its 

abundance at either Marathon or Long Key was observed 

during the study. 

Figure 5. Opportunistic sponge species exhibiting rapidly 

increasing and decreasing abundance (average number/

transect ± S.E. bars). The shaded area (shown on Figures 

5A and 5G) depicts timing of 1991–1993 bloom events at 

both sites. Large arrows (shown on Figure 5A) represent 

timing of bloom events in 1994 and 1995 in the vicinity of 

Long Key and smaller arrows represent timing of blooms in 

Florida Bay that might have affected Long Key area. The 

star represents the timing of Hurricane Wilma. 

H

Figure 6. Sponges that gradually declined in abundance 

(average number/transect ± S.E. bars). The shaded area 

depicts timing of 1991–1993 bloom events at both sites. 

Large arrows represent timing of bloom events in 1994 and 

1995 in the vicinity of Long Key. Smaller arrows represent 

timing of blooms in Florida Bay that might have affected 

Long Key area. The star represents the timing of Hurricane 

Wilma. 
Stevely, J.M. et al. GCFI:63 (2011) Page 393

Callyspongia (Cladochalina) vaginalis — The branching 

vase sponge (Table 3) - a highly characteristic greyishlavender, conulose, tube-shaped sponge, also typically 

sedimented (Alcolado 2007) - was uncommon at Marathon 

and extremely rare at Long Key. Because its abundance 

was low, no discernable abundance pattern or statistical 

trend was established.

Effects of Hurricane Wilma 

The most influential of the two hurricanes that brought 

tropical storm-strength and hurricane-force winds throughout the study area after the 2005 survey work was completed was Hurricane Wilma, which had maximum sustained 

wind speeds estimated at nearly 105 knots (Category 3 

intensity) when landfall occurred in southwestern Florida 

near Cape Romano on 24 October 2005. Table 4 describes 

the typical morphological characteristics of each species 

and our assessment of the principal agent(s) for their 

decline in abundance due to hurricane effects. The sponge 

population at Marathon was highly affected by Hurricane 

Wilma (Figure 3). Between 2005 and 2006, total abundance and the abundances of 13 species (Table 4) significantly decreased. In contrast, Hurricane Wilma had little 

effect at Long Key; only one species (N. erecta) declined 

significantly in abundance. Interestingly, two species 

increased significantly in abundance following Hurricane 

Wilma--Aplysina fulva at both Marathon and Long Key 

and X. subtriangularis at Marathon. Overall, species with 

strong attachments to the substrate, including large or 

massive species, were damaged the least. Sponges with 

weak attachments, branching growth patterns, fragile 

structures, or high profiles were damaged by the hurricane 

to the point that their abundances were significantly 

diminished. High-profile species with complex structures 

of some type, fragile skeletons, and weak attachments were 

the most vulnerable.

DISCUSSION

Do Synechocococcus Bloom Conditions Kill Sponges? 

A direct causal link between the blooms and mode of 

sponge death has not been established (Butler et al. 1995, 

Lynch and Phlips 2000, Peterson et al. 2006). Previous 

reports of sponge mass mortality have not been associated 

with blooms of planktonic cyanobacteria such as Synechocococcus spp. Although such blooms can be toxic to 

marine animals (Mitsui et al. 1989), there was no noticeable mortality of fish or invertebrates during the 1991 - 1993 

sponge mortality events (Butler et al. 1995). 

Butler et al. (1995) suggested the possibility that the 

exceptionally dense and persistent blooms of Synechococcus spp. in the Florida Keys impaired the filtration and 

feeding mechanisms of sponges. In laboratory experiments 

(Lynch and Phlips 2000), three sponge species (including 

H. melanadocia, and S. vesparia) present in their study 

area were exposed to bloom-level densities of both natural 

and laboratory-cultured Synechococcus for the relatively 

short duration of up to five days. They did not die; the 

sponges were able to filter the Synechococcus spp. 

However, clearance rates from surrounding water by 

sponges showed some decline over time, indicating that 

longer-term exposures might ultimately lead to mortality. 

During our study, the bloom events were persistent, some 

lasting for 6 - 8 months.

Many cyanobacteria, including Synechococcus spp., 

are known to excrete a sticky carbohydrate polymer in 

prodigious quantities (Phlips et al. 1989). Although, under 

laboratory conditions, the production of this polymer was 

reduced compared with the rate of production in the natural 

environment, polymer production was enhanced by highsalinity conditions such as those present in the early 1990s 

(Swart et al. 1999) where the bloom was initiated (Lynch 

and Phlips 2000). It seems probable that the laboratory 

experiments were unable to duplicate the duration and 

nature of the bloom conditions experienced by individual 

sponges in nature. It is possible that high concentrations of 

polymer occluded sponge canals, ‘starving’ the sponge 

mesophyl, causing stress, and leading to localized infection 

and subsequent necrosis of sponge tissue. 

Stress that can destroy weakened sponges has been 

implicated in sponge viral (Vacelet and Gallissian 1978), 

bacterial (Vacelet et al. 1994), cyanobacterial (Rützler 

1988) and fungal infections. Previous instances of mass 

sponge mortalities in the Caribbean, Gulf of Mexico, and 

the Mediterranean have been attributed to a variety of 

sponge infections (Lauckner 1980, Peters 1993), sometimes in response to environmental stress. Moreover, 

commensal bacteria that normally digest necrotic sponge 

tissue may become virulent and digest living tissue under 

unfavorable environmental conditions (Vacelet et al. 1994).

Figure 7. Sponges that increased in abundance after 

Hurricane Wilma (average number/transect ± S.E. bars). 

The shaded area depicts timing of 1991–1993 bloom events 

at both sites. Large arrows represent timing of bloom 

events in 1994 and 1995 in the vicinity of Long Key. Smaller 

arrows represent timing of blooms in Florida Bay that might 

have affected Long Key area. The star represents the 

timing of Hurricane Wilma.
Page 394 63rd Gulf and Caribbean Fisheries Institute 

Table 4. Effects of hurricanes on sponge abundance at Marathon and Long Key. Tukey’s: P < 0.05; SNK: P < 0.05; 

Dunn’s: P < 0.05; T-test: P < 0.05; Mann-Whitney: P < 0.05. Significance columns indicate the test(s) that established statistically valid differences. Dash: Not present in transects at this study site.

Species Morphological Hurricane effect Marathon Long Key

Change in 

abundance

Significance Change in 

abundance

Significance

Spheciospongia 

vesparium

Massive, low profile, broad 

base, tough, strong attachNo change No change

Cliona varians Thick clubs, broad base, No change No change

Ircinia campana Massive vase, elastic, flexible, 

weak attachment

Detachment, and 

transport off-site

Decrease SNK No change

Ircinia felix Branching mass, weak attachment

Detachment, and 

transport off-site

Decrease SNK No change

Ircinia strobilina Massive, narrow base, 

weak attachment 

(rollers common)

Detachment, and 

transport off-site

Decrease SNK No change

Hippospongia lachne Massive, squat, broad base, 

tough, strong attachment

No change No change

Spongia barbara Massive, tough, 

strong attachment

─ No change

Spongia barbara dura Columnar (high profile), weak 

attachment

Detachment, and 

transport off-site

Decrease SNK No change

Spongia graminea Massive, tough, strong 

attachment

No change ─

Cinachyrella alloclada Small, low profile, broad, Scouring and burial Decrease Tukey’s, SNK No change

Halichondria melanadocia

Small, fragile, low profile, 

weak attachment

Scouring or burial 

and pulverization

Decrease SNK No change

Adocia implexiformis Stringy, fragile, relatively high 

profile, weak attachment

Pulverization, fragmentation, and Decrease Tukey’s, SNK No change

Lissodendoryx 

isodictyalis

Small, fragile, low profile, 

weak attachment

Pulverization Decrease Tukey’s, SNK No change

Chalinula molitba Fragile, weak attachment Pulverization Decrease SNK No change

Niphates erecta Branching, firm, weak 

attachment

Pulverization, fragmentation, and 

transport off-site

Decrease Tukey’s, SNK Decrease SNK

Hyrtios proteus Small, low profile, broad base, 

strong attachment

Scouring and 

burial

Decrease SNK No change

Amphimedon viridis Branching, firm, weak attachment

Pulverization and 

transport off-site

Decrease SNK No change

Petrosia cf pellasarca Amorphous, fragile, weak 

attachment

Pulverization and 

transport off-site

Decrease T-Test ─

Tedania ignis Small, soft, low profile, 

weak attachment

No change No change

Aplysina fulva Thin branching, tough, elastic, 

multiple weak attachments

Fragmentation and 

re-attachment

Increase SNK Increase SNK

Xestospongia subtriangularis

Branching mass, firm, brittle 

texture, 

multiple weak attachments

Fragmentation and 

re-attachment

Increase Mann-Whitney ─

Tectitethya crypta2

Large, low profile, 

strong attachment

No change No change

Callyspongia 

vaginalis2

Tube-shaped, 

weak attachment

No change ─
Stevely, J.M. et al. GCFI:63 (2011) Page 395

The widespread disappearance of sponges in the 

Florida Keys and Florida Bay that we witnessed from 1991 

through 1993 was dramatic. A major decline in overall 

abundance and biomass occurred at both Marathon and 

Long Key during the two major bloom events between 

1991 and 1993, and sponge biomass remained at a reduced 

level for a considerable period--at least 10 – 15 years. 

Moreover, the timing of recruitment differed at both sites; 

recruitment of specific species at Long Key often consistently lagged that at Marathon. For most of the larger longlived species, a significant period of time elapsed before 

recruitment was visible at both sites. Finally, patterns of 

decline in sponge abundance and the patterns of response 

or recovery were not necessarily the same within a species 

between sites. 

If we compare the dynamic nature of the spatial extent 

and duration of the 1991 - 1993 blooms with the patterns 

and timing of sponge mortality we observed, it is clear that 

the bloom conditions were somehow the principal cause of 

the sponge mortality during that time. Many of our 

findings support this conclusion:

i) All species surveyed over the initial bloom events 

(1991 - 1993) were essentially eliminated at both 

locations.

ii) Recruitment of several species at Long Key 

lagged behind their recruitment at Marathon, a 

feature consistent with the continued exposure of 

the Long Key site to repeated bloom events after 

1993.

iii) Several opportunistic species increased explosively in abundance upon cessation of bloom 

conditions at both Marathon and Long Key, 

possibly because of reduced competition for space 

and food caused by the demise of large specimens 

that predominated in these sites.

Further supporting our conclusions, Butler (2008) 

reported a re-occurrence of sponge deaths in association 

with new bloom conditions in 2007. Again, no sponge 

mortality was reported outside of the bloom area. 

Patterns of Response

All species surveyed over the initial bloom period 

were essentially eliminated. Significant recruitment did 

not occur in many species until after cessation of the major 

blooms in 1995. Because the responses of individual 

species to bloom conditions followed several general 

patterns, recovery from the blooms produced a complex 

picture of sponge community dynamics in space and time. 

Rapid Decline and Gradual Recovery — Nine large 

species (S. vesparium, C. varians, I. campana, I. felix, I. 

strobilina, H. lachne, S. barbara, S. barbara dura, and S. 

graminea) that predominated in the sponge community 

prior to 1991 and were monitored in this study from 1991 

or 1993 recovered to some degree over the course of the 

study. These species are long-lived, stable components of 

other tropical west-central Atlantic environments (Hechtel 

1965, Wiedenmayer 1977, Van Soest 1978, 1980, 1984, 

Zea 1987). Spheciospongia vesparium, C. varians, I. felix, 

I. strobilina, and S. barbara dura showed consistent and 

pronounced increases in abundance at Marathon, but 

exhibited either delayed or less pronounced increases at 

Long Key. The differences in recovery between areas may 

be, in part, due to the unpredictable nature of larval 

dispersal and survival, the usually more adverse salinity 

and temperature conditions in waters of close proximity to 

Florida Bay [greater seasonal and interannual extremes 

(Swart and Price 2002), to the point of lethality to invertebrate larvae or postlarvae (e.g., Bert et al. In preparation)], 

the greater exposure of the Marathon area to open ocean 

waters, or the prolonged and repetitious bloom conditions 

at Long Key from 1991 through 1997. Bloom-laden water 

was spread to adjacent parts of the bay by strong seasonal 

cold fronts, which promote water outflow from Florida Bay 

into adjacent waters (Lee and Smith 2002). The prevalent 

water flow patterns during winter would have brought the 

intermediate-concentration bloom waters described by 

Phlips et al. (1999) into close proximity to our Long Key 

site. Thus, it seems that Marathon was affected only by the 

two major blooms, whereas Long Key likely was affected 

by bloom waters over a more prolonged period of time 

(1991 - 1997). 

The length of time required to observe recruitment of 

the normally conspicuous S. vesparium seems quite 

remarkable in that, at both study areas, aggregations that 

survived bloom conditions were located only 1 - 3 km from 

decimated aggregations. Moreover, recruitment at Long 

Key lagged that at Marathon by about five years despite 

the presence of large individuals that had recovered from 

bloom conditions within the study area, whereas all 

individuals had been eliminated from Marathon. Size data 

for S. vesparium at Long Key compared with that at 

Marathon indicates that initial recovery at Long Key was 

via regeneration of individuals not completely killed during 

the initial bloom, rather than recruitment via sexual 

reproduction and larval dispersal. In a recent study near 

Long Key, Donahue (2008) transplanted S. vesparium and 

other species into areas depopulated of sponges and into an 

area with a well-established sponge community unaffected 

by bloom conditions. He found that S. vesparium and 

some other species had significantly faster growth rates in 

the depopulated areas and suggested that this resulted from 

decreased competition for food.

Several features of C. varians, I. felix, I. strobilina, 

and S. barbara dura may have been conducive to their 

increase in abundance at Marathon. Increased availability 

of substrate for colonization and decreased competition for 

food may have allowed these species to thrive. C. varians

is apparently very hardy; it can thrive even in polluted 

waters (Alcolado 2007). I. felix can grow rapidly and 

overgrow other sponge species, probably because it 

harbors a photosynthetic cyanobacteria symbiont 
Page 396 63rd Gulf and Caribbean Fisheries Institute 

(Wilkinson and Cheshire 1988) and has chemical defenses 

against predation (Freeman and Gleason 2010), as does I. 

strobilina (Waddell and Pawlik 2000).

The formerly abundant I. campana was a major 

component of total sponge community biomass prior to 

bloom conditions (Stevely et al. 2010). However, it did 

not recruit to the area for a decade after it was decimated; 

and it was present at only a small fraction of its former 

abundance at both areas 13 years after the initial bloom. 

Of all the major long-lived species found in the study area, 

I. campana appeared to have the most limited ability to 

recover. Ircinia campana is a chemically defended sponge 

that heals very slowly (Walters and Pawlik 2005). If badly 

damaged, individuals may die rather than recover. 

Similarly to the situation for I. campana, H. lachne

recovered only slightly in our study areas; but it was 

sufficiently abundant at other locations affected by the 

algal blooms to support commercial harvest. Spongia 

graminea also recovered only partially compared with its 

1991 abundance.

Fluctuating abundance — After cessation of bloom 

conditions, and removal of the dominant food and space 

competitor species at both Marathon and Long Key, 

several species increased explosively in abundance, 

indicating an “‘opportunistic” life history strategy. Nine 

species (Figure 5) were observed to have population 

fluctuations that would suggest an opportunistic life history 

strategy, with significant increases and decreases in 

abundance during the study. Cinahyrella alloclada, H. 

melanadocia, L. isodictyalis, C. molitba, and N. erecta

exhibited highly opportunistic patterns of changing 

abundance at both Marathon and Long Key throughout the 

study.

Cinachyrella alloclada is considered to be an opportunistic species in Cuban waters (Pedro Alcolado, Instituto 

de Oceanolgia, Pers. communication) because its principal 

mode of reproduction at some locations is the extrusion of 

numerous tiny sponge buds, which are locally dispersed, 

resulting in a clustered distributional pattern of small, 

closely clumped individuals. This mode of reproduction 

can lead to rapid increases in numbers of individuals and 

the clumped distribution (Rützler and Smith 1992) we 

observed in the field.

Two species, A. implexiformis and H. proteus, showed 

a different pattern of abundance between the two sites. At 

Marathon, these species widely varied in abundance during 

the study; whereas, at Long Key, they both showed a 

gradual decline in abundance. Taken as a whole, this 

group provides an example of the complexity of sponge 

community dynamics in space and time. Individually, 

species may not show the same pattern at different sites 

over the same period of time, indicating that a variety of 

factors other than bloom conditions can influence their life 

histories.

Gradual Decline — Three species (H. proteus, A. implexiformis, and T. ignis) generally exhibited a gradual decline 

in abundance from 1995 forward, to the point that they 

were uncommon at Long Key. One explanation for this 

general demise is that, with the increasing recruitment of 

other species into Marathon and Long Key over the latter 

part of the study period, opportunistic species such as 

Tedania ignis could no longer compete for food and space. 

Tedania ignis can reclaim bared space, is a fast grower, and 

can overgrow other species; but it is a poor recruiter to bare 

substrate and is vulnerable to predation (Wulff 2006b, 

2010), which could contribute to a long-term decrease in 

abundance. 

Low Abundance, No Change — The abundance of T. 

crypta and C. vaginalis at Marathon, and of H. proteus and 

T. ignis at Long Key were very low throughout the periods 

during which they were monitored. Butler (2008) reported 

that T. crypta was relatively resistant to bloom conditions, 

which might explain its persistence in low numbers. The 

observed pattern for T. ignis at Long Key contrasts with 

that seen at Marathon where it was relatively abundant 

when first included in the surveys.

Like other Hadromerida such as Spheciospongia 

vagabunda (Kelly 1986, Kelly and Bergquist 1988), S. 

vesparium, and Tethya spp., T. crypta can cease pumping 

for considerable periods of time (Reiswig 1971), which 

also may provide some protection against bloom conditions. Similarly, the sediment-covered surface of T. crypta

may act as a filtration barrier, as it does for C. alloclada. 

Reiswig (1973) concluded that T. crypta establishes stable 

local populations and has several life history adaptations to 

insure the longevity of individuals. However, due to less 

investment in large, energetically expensive larvae, they 

are unable to rapidly colonize newly available substrate 

within their local area. The persistent low abundance we 

observed is consistent with Reiswig’s (1973) conclusions. 

Callyspongia vaginalis is a slow grower that is not 

easily fragmented. It relies on the production of many 

larvae for colonization (Leong and Pawlik 2009); but, 

despite its potential for larval dispersal, its population 

genetic structure indicates that most dispersal is highly 

localized (DeBiasse et al. 2010). Although is can be 

common in some communities (Waddell and Pawlik 2000), 

it has no chemical defenses against at least some predators 

(Walters and Pawlik 2005). This poor defense system and 

dispersal ability may limit its abundance in areas where 

competition for substrate is strong.

Species Responses to Hurricane Wilma 

After Hurricane Wilma, overall sponge abundance was 

significantly lower at Marathon but not at Long Key. 

Many species at Marathon were markedly reduced in 

abundance. Many species damaged at Marathon had low 

abundance at Long Key, precluding clear detection of 

significant changes in abundance. Conditions at Long Key 
Stevely, J.M. et al. GCFI:63 (2011) Page 397

during Hurricane Wilma were slightly less severe than at 

Marathon (K. Kasper, National Oceanic and Atmospheric 

Administration, Pers. communication), and protection 

from open the Gulf of Mexico wave energy present at 

Marathon made a large difference in overall sponge 

survival at Long Key. Slight differences in reef orientation 

to storm waves can dramatically change the effect of a 

hurricane on sponge abundance (Wulff 1995).

Massive individuals of the long-lived species with 

strong attachments to the substrate (S. vesparium, C. 

varians, H. lachne, S. barbara, S. graminea) were 

remarkably resilient to hurricane conditions, even in 

shallow water. Apparently the survival strategy of these 

species is to resist wave action as single, stable individuals 

rather than to utilize wave action to divide single individuals into multiple fragments that can quickly attach to and 

colonize denuded substrates. 

Many significant declines in abundance occurred in 

long-lived, massive species with weak or proportionally 

small attachments (I. campana, I. felix, I. strobilina) or 

branching or columnar forms (S. barbara dura) or in 

opportunistic species (C. alloclada, H. melanodocia, A. 

implexiformis, L. isodictyalis, N. erecta, H. proteus, A. 

viridis, P. cf. pellasarca). These species were either 

pulverized or fragmented by wave action or detached by 

sand scouring. These types of species are prone to 

hurricane damage (Wulff 2006a). They may be more 

adapted to recolonizing barren substrate following storms 

than are the massive sponges with strong attachments. 

Some may even generate propagules from small fragments 

or have the capacity to re-aggregate into elemental sponges 

from loose groups of cells (Maldonado and Uriz 1999). 

Others may rely on wave action for fragmentation as their 

principal method of reproduction as well as for dispersal 

(Leong and Pawlik 2009).

Wulff’s (1995) evaluation of the impacts of Hurricane 

Joan (October 1988) on A. fulva, Iotrochota birotulata, 

and Amphimedon rubens, provides further insight into the 

pattern of mortality observed in this study. In Wulff’s 

(1995) study, almost half of the individuals and biomasses 

of numerous species were lost during the hurricane.

Aplysina fulva, one of the two species in our study to 

significantly increase in abundance after the hurricane, 

suffered less loss in abundance in Wulff’s (1995) study 

than did the other two species, in part because A. fulva’s 

skeleton is composed of a tight mesh of spongin and the 

mesohyl is permeated with fibrillar collagen, conferring 

tremendous elasticity and flexibility to the sponge body. 

In contrast, X. subtriangularis, the other species that 

significantly increased in abundance after Hurricane 

Wilma, was fragmented because its relatively brittle, 

dense, spicule skeleton bound by nodal spongin is easily 

fragmented, but the fragments re-attach to stable substrate 

after they are immobilized.

The pattern of mortality resulting from the effects of 

Hurricane Wilma differed notably from the pattern 

resulting from the plankton blooms. The several massive 

species were resistant to the effects of Hurricane Wilma (S. 

vesparium, C. varians, H. lachne, S. graminea); but these 

species were decimated by plankton blooms. Because 

those species account for high percentages of total sponge 

community biomass, the blooms would have a greater 

impact on total sponge biomass than would hurricanes. 

Furthermore, many of the Marathon species that were 

affected by the hurricane tended to be species that could 

rapidly recolonize an area (C. allocolada, H. (H.) melanadocia, A. implexiformis, L. isodictyalis, C. molitba, N. 

erecta, H. proteus, A. virdis). Consequently, the impact of 

Hurricane Wilma on sponge community biomass would 

also be more short-term in nature. Although most studies 

of hurricane effects on sponge community diversity and 

biomass are limited by a lack of pre-storm population data 

(Rützler 2004), studies by Fenner (1991), Wulff (1995), 

and Cropper and DiResta (1999) have shown relatively 

rapid recovery (within two years) of sponge populations 

following hurricane conditions. Local geomorphology and 

hurricane intensity will significantly affect the severity of 

hurricane damage, but our data illustrate the tenacity of 

some sponges, even in shallow water subjected to full 

hurricane force conditions. 

Ecological Implications

The driving force behind the occurrence of repeated 

and sometimes widespread Synechococcus blooms in the 

middle and upper Keys is not clear. Nor is the extent of 

anthropogenic influences causing or exacerbating the 

blooms. It is clear that sponge community biomass takes 

more than decade to recover to pre-mortality biomass, and 

species’ relative abundances can change unpredictably and 

dramatically. Even if Synechoccus blooms occur relatively 

infrequently in the future--for example, every 15 - 20 years

--our study shows that such repeated episodes will result in 

chronically reduced sponge community biomass and in 

altered, shifting species composition and relative abundance in the mid and upper Florida Keys. Chronic 

reduction in sponge community biomass, species abundance, and species composition in that area could have 

substantial ecological and fishery impacts. 

In contrast to hurricanes and possibly sporadic sponge 

disease episodes, algal blooms severely reduce sponge 

biomass and thereby the overall ability of the local sponge 

community to filter water. Sponge diseases can also have 

pronounced effects on sponge biomass and species 

composition (Gochfeld et al. 2007, Wulff 2007), but are 

relatively rare in water of good quality and are typically 

restricted to certain species groups. For example, mortality 

of commercial bath sponges attributed to sponge diseases 

in Florida, the Caribbean, and the Mediterranean has been 

reported only infrequently (Brice 1898, Allemand-Martin 

1914, Smith 1941, Vacelet 1994). 
Page 398 63rd Gulf and Caribbean Fisheries Institute 

Sponges filter large volumes of water and are very 

efficient in retaining small food particles (particularly < 5 

μ) to meet their nutritional requirements (Reiswig 1971, 

Riisgard et al. 1993, Weisz 2006). In sponge dominated 

habitats, it is likely that sponges can significantly reduce 

picoplankton concentrations in the water column (Pile 

1997, Pile et al. 1997), particularly in shallow water 

habitats (Riisgard et al. 1993). Lynch and Phlips (2000) 

estimated that the loss of biomass in Florida Bay sponge 

community would significantly lengthen the time required 

for removal of plankton from the water column. Thus, 

chronic sponge community biomass loss, such as that we 

saw from the Synechoccus blooms, would likely affect the 

dynamics of plankton communities, with potentially broad 

ecological consequences (Lynch and Phlips 2000). 

Moreover, the loss of sponge biomass caused by bloom 

conditions may have generated a feedback loop by 

rendered the Florida Bay ecosystem susceptible to 

reoccurring cyanobacteria blooms (Peterson et al. 2006).

CONCLUSIONS

Our detailed and long-term data indicate that, for the 

sponge communities in the middle to upper Florida Keys, 

assessment of population recovery by measuring only 

numerical abundance can be misleading. Our results 

clearly showed the bloom impact on sponge community 

biomass was much greater than the impact indicated by 

numerical counts. However, the patterns of response 

exhibited by individual species show that there are many 

different patterns of change in abundance. The sponge 

assemblage at any one time may differ from that of another 

time, even on a relatively short-term basis. While other 

deeper-water sponge communities have been shown to be 

stable with little change over long periods of time (Pansini 

and Pronzato 1985), we saw a much different picture for a 

shallow-water sponge community. Species respond in 

different ways at different sites, and population change is 

dynamic, sometimes dramatic, and sometimes unpredictable. The fact that the system is dynamic is not as surprising because shallow water sponge communities of the 

Florida west coast are subjected to aperiodic perturbations 

(highly localized salinity events, hurricanes, harmful algal 

blooms, and disease). Indeed, in recent literature there is 

evidence that sponge assemblages are highly dynamic 

(Bell et al. 2006, Carballo, et al. 2008).

However, we can meaningfully discuss recovery, 

particularly from a resource management perspective, 

when looking at sponge community biomass. Those 

species that dominate sponge community biomass are large 

and appear to be long-lived. If these species are able to 

recruit and attain their former levels of abundance and size, 

then the ecological function of the sponge community, in 

terms of filter feeding capacity and providing structural 

habitat, will have been restored. However, after bloom 

events, this is not a rapid process for all species; restoration 

of sponge population biomass in our study area was at least 

a 10 - 15 year process. 

ACKNOWLEDGEMENTS

Funding was provided by the Florida Fish and Wildlife Conservation Commission, Florida Sea Grant College Program, Cantonis Marine 

Science Endowment, and Florida Keys National Marine Sanctuary 

Program. This study would not have been possible without the field 

assistance of Chuck Adams, Bob Wasno, and the staff of the Florida Keys 

Marine Laboratory. We are also grateful to Pedro Alcolado, Shirley A. 

Pomponi, and Klaus Rützler for sponge taxonomic assistance and 

encouragement and to Carlos Martinez for the Spanish translation of the 

abstract. Over the years, many colleagues in the sponge biology 

community that we met at several international sponge biology 

conferences graciously provided advice and encouragement. The authors 

thank the National Institute of Water and Atmospheric Research for 

supporting sabbatical leave for J.S. to complete a first draft of the 

manuscript. M.K. was supported by NIWA’s FRST-funded Biodiversity 

and Biosecurity Programme.

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