Potential biogenic habitat alteration by OCS Activities 

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FINAL TECHNICAL SUMMARY 

STUDY TITLE: Potential biogenic habitat alteration by OCS Activities: Adverse effects to 

early life-stages of giant kelp from chronic disturbance 

REPORT TITLE: Potential biogenic habitat alteration by OCS Activities: Adverse effects 

to early life-stages of giant kelp from chronic disturbance 

CONTRACT NUMBER: 14-35-0001-30471 

SPONSORING REGION: Pacific 

APPLICABLE PLANNING AREAS: Southern California 

FISCAL YEAR(S) OF PROJECT FUNDING: June 1, 1991 through May 31, 1993 

COMPLETION DATE OF REPORT: March 2003 

COST(S): FY - 91 - $50,694; FY 92 - $55,186; FY 93 – no cost 

CUMULATIVE PROJECT COST: $105,880 

PROJECT MANAGER: Russell J. Schmitt 

AFFILIATION: University of California, Santa Barbara 

ADDRESS: Coastal Research Center, Marine Science Institute, University of California, 

Santa Barbara, CA 93106-6150 

PRINCIPAL INVESTIGATORS: 

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Daniel C. Reed, 2Alfred W. Ebeling, and Michael 

Neushul (deceased) 

ADDRESSES: 

1

Marine Science Institute, University of California, Santa Barbara, CA 

93106-6150; 2

P.O. Box 1135, Bandon, Oregon 97411 

KEY WORDS: attachment, barium, behavior, Carpinteria, colonization potential, dispersal, 

giant kelp, ecological impact assessment, fertilization, immigration, Macrocystis pyrifera, 

nonpolar organic compounds, petroleum hydrocarbons, produced water, propagules, 

recruitment, salinity, settlement, southern California, swimming, toxins, zoospore 

BACKGROUND: For both ecological and economic reasons, giant kelp (Macrocystis 

pyrifera) forests form the most important biogenic habitat in the nearshore coastal waters of 

the Pacific OCS region. Various OCS oil and gas activities, however, may adversely affect 

these prominent marine communities. In particular, chronic exposure to production 

discharges (e.g. produced water) and petroleum hydrocarbons may have persistent long-term 

effects on the dynamics of giant kelp populations. Although the adult macroscopic 
Final Technical Summary – Reed et al. 

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sporophyte stage may be relatively invulnerable to acute exposure to spilled oil, there is 

growing evidence that the microscopic stages are susceptible to several forms of pollution at 

very low levels. Consequently, forests of giant kelp ma be at risk to acute and chronic 

exposure to constituents in oil and produced water, which inhibit kelp recruitment 

OBJECTIVES: Like all kelps, Macrocystis has a heteromorphic life-history in which motile 

spores settle on the bottom and germinate into free- living male and female gametophytes that 

produce eggs and sperm. A highly volatile pheromone produced by the egg causes the release 

and attraction of the sperm to the egg. The embryonic sporophytes developing from the 

fertilized egg ultimately becomes the macroscopic sporophyte with a characteristic kelp-like 

form. Low levels of refined oil have been shown to inhibit spore germination, gametogenesis, 

and early sporophyte development in the Atlantic kelp laminaria saccharina. Produced water 

effluents contain many heavy metals, some of which may later spore settlement and 

gametophyte reproduction if their concentrations are elevated above background levels in the 

water column. More importantly, the highest concentrations of pollutants are found on the 

bottom where metals and petroleum hydrocarbons accumulate in sediments near discharges. 

Such benthic accumulation of pollutants could severely alter patterns of kelp recruitment, 

especially since kelp beds growing on soft sediments are common near oil and gas 

development activities. 

Our objective was to determine potential lethal and sublethal effects of discharges from oil 

and gas activities on growth and reproduction in the microscopic recruitment stages of giant 

kelp. Our goal was to predict the level at which effects would be noticeable in natural 

populations of giant kelp that are chronically exposed to produced water and petroleum 

hydrocarbons. 

DESCRIPTION: Laboratory experiments were used to determine how water column 

exposure to produced water influences the colonization potential of giant kelp zoospores on 

the bottom. These experiments were designed to examine effects of produced water 

concentration and exposure duration on: (1) swimming duration of zoospores, (2) attachment 

ability of zoospores, and (3) germination of gametophytes from zoospores. Zoospores were 

maintained in suspension at relatively low densities in 18 L containers and exposed to one of five 

concentrations of produced water for varying amounts of time. Field experiments were used to 

determine the spatial scale of benthic effects of an active produced water outfall on various 

components of recruitment in the giant kelp. Field experiments were done in he shallow 

subtidal of a high energy open coast near Carpinteria CA, USA (34°23'N, 119°30'W). The 

outfall diffuser of produced water studied was located ≈ 200-300 m offshore in a sandy bottom at 

a depth of about 11 m that was approximately 200 m downcurrent from a giant kelp forest. The 

response variables measured in the field experiments were: zoospore production in transplanted 

sporophytes, survival, reproduction, and sporophyte production of outplanted gametophytes. 

 

STUDY RESULTS: Zoospore swimming generally decreased with increasing produced water 

concentration and exposure duration; however, the specific pattern of decrease differed between 

experimental trials done on different dates. The effect of exposure duration on the ability of 

swimming zoospores to attach to plastic dishes placed on the bottom varied with produced water 

concentration. Zoospores placed in produced water concentrations of 1% and 10% showed a 
Potential biogenic habitat alteration by OCS Activities 

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steady decline in their ability to attach with increased exposure; lower concentrations of 

produced water had no such effects. The percentage of zoospores that germinated after 

attachment varied tremendously with exposure duration and date of experimental trial. 

Zoospores that settled during the first 12 h after release had very poor rates of germination 

indicative of a short precompetent period. Surprisingly, exposure of suspended zoospores to 

high concentrations of produced water during the first 12 h reduced this precompetent period and 

greatly improved germination success on the bottom. The magnitude of this enhancement, 

however, varied among dates. 

Discernible effects on all parameters measured in the field were limited to areas very close to the 

outfall (i.e. < 50 m). Zoospore production in sporophytes transplanted to varying distances from 

the diffuser did not vary in a systematic way. Survival and successful reproduction (i.e. 

sporophyte production) of outplanted gametophytes varied significantly among experimental 

dates. Performance of these parameters was significantly reduced only at the site nearest the 

diffuser (i.e. 5 m away). Poor gametophyte survival near the outfall may have resulted from 

exploitative competition with Beggiatoa sp. (a fast growing filamentous marine bacteria that 

exploits areas high in hydrogen sulfide, an abundant constituent of the produced water effluent) 

rather than from toxicity of produced water. Laboratory assays indicated that gametophyte 

reproduction and subsequent sporophyte production were inhibited at levels likely to occur 

within the near vicinity of the diffuser. Nonetheless, field data indicate that the lack of 

sporophyte production observed near the diffuser probably resulted from factors affecting 

gametophyte survival. 

SIGNIFICANT CONCLUSIONS: Our laboratory experiments indicatde that the toxicity of 

produced water to giant kelp zoospores is generally low. Relatively high concentrations of 

produced water (≥ 1 %) were needed to produce adverse effects on zoospore swimming, 

attachment, and germination. Moreover, with the exception of swimming, adverse effects of 

produced water were observed only after relatively long periods of exposure (i.e. ≥ 24 h). 

Interestingly, relatively short exposures to high concentrations of produced water actually 

promoted successful germination during what normally appeared to be a pre-competent period in 

all three experimental trials. How produced water could cause this unexpected pattern of early 

germination, however, remains unknown. It is possible that zoospore swimming is more 

sensitive to produced water than our results indicate. We may have underestimated the number 

of non-swimming zoospores in treatments containing produced water if toxins in the effluent 

inactivate flagella without causing the spore to change shape. We cannot be certain that all 

zoospores induced into a non-swimming mode by produced water changed from pear shaped to 

spherical. However, we never saw non-swimming zoospores that were not spherical in video 

recordings of zoospores placed in different concentrations of produced water 

Results from our field experiments indicated that discernible effects on kelp recruitment are 

likely to be limited to areas very close to produced water outfalls; significant reductions in 

gametophyte survival and reproduction (measured as sporophyte production) were observed only 

as far as our site located 5 m from the outfall. However, data from this study alone are 

insufficient to implicate the discharge of produced water as the primary cause for these observed 

effects. Constraints on the design of our field experiments prevented us from completely 

isolating natural causes of spatial variability from that due to the discharge of produced water. 

There are compelling reasons to believe, however, that the discharge was the primary mechanism 
Final Technical Summary – Reed et al. 

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causing reduced performance in giant kelp. First, the results were highly localized within a 

relatively large and uniform area. Second, the observed patterns were symmetrical about the 

diffuser in as much as the most distant locations on either side of the outfall (which were chosen 

to serve as controls) were similar and different from that observed near the diffuser. Lastly, 

companion studies done at Carpinteria using other organisms showed that previously observed 

effects dissipate during brief periods when the discharge is not operational. 

STUDY PRODUCTS: The following peer-reviewed publications resulted from this work. 

Reed, D.C. and R.J. Lewis. 1994. Effects of an oil and gas production effluent on the 

colonization potential of giant kelp (Macrocystis pyrifera) zoospores. Marine Biology

119: 277-283. 

Reed, D.C., R. J. Lewis, and M. Anghera. 1994. Effects of an open coast oil production 

outfall on patterns of giant kelp (Macrocystis pyrifera) recruitment. Marine Biology

120: 26-31. 

Raimondi, P.T. and D.C. Reed. 1995. Determining the spatial extent of ecological impacts 

caused by local anthropogenic disturbances in coastal marine habitats. Pages 179-198, 

In R.J. Schmitt and C.W. Osenberg (eds.). Detecting Ecological Impacts: Concepts 

and Applications in Coastal Habitats, Academic Press, San Diego.