# Center for Lakes and Reservoirs Environmental Science a nd Management Programs Assessing Hull Fouling as a Vector of Invasive Species: A Case Study in the Lower Columbia River

Contact Information

Ian Davidson idavidso@pdx.edu Portland State University Center for Lakes and Reservoirs PO Box 751 - ESR Portland OR 97207-0751 Ph: 503-725-8104 Fax: 503-725-3834


## Introduction

Q: What is the extent and composition of hull biofouling entering the Columbia River ? Does this vector pose a significant thre at of invasion to the system?

Shipping has been identified as the major ve ctor of organism transfers on a global scal e. Of the two sub-vectors associated wit h shipping, there has been huge bias in ecological resear ch toward ballast-mediated transfers of organisms, perhaps at the expense of hull fouling. Hull fouling transfers of organisms are historically and contemporaneously importa nt in aquatic nonindigenous species ( NIS ) introductions, yet very little quantitative da ta exist to rigorously examine the curren t rates, extent and composition of organ ism transfers via vessel hulls.

Research at Portland State University has shown that eight of the 81 established introduced species in the Lower Columbia River were possibly hull mediated invasions. Analysis of shipping patterns , hull fouling loads and biofouling organism ecology will provid e an insight into current rates of biofouling tr ansfers and the possibility of future succ essful invasion resulting from this vector . The data may be used to implement management strategies to reduce the risk of hull transfers into and out of the Lower Columbia River .

Ian Davidson sampling hull biofouling on the waterline of a barge on dry dock. 

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## Personnel:

Primary: Ian Davidson (Principal I nvestigator and project Coordinato r), Mark Sytsma (Principal Inve stigator), Greg Ruiz (Princi pal Investigator)

Additional field and database a ssistance: Christina Simkanin



## Funding/collaborators:

The US Coast Guard is funding the work as part of the CRANSI program.

Whitman Miller, at SERC, is a collaborator

An example of a bulk carrier on dry dock at the ship yard in Portland (left). Notice a clump of fouling (hydroids) on the hull in an area where antifouling paint could not be previously applied because of dry docking blocks (right).



## Accomplishments/results:

There are four avenues of rese arch being pursued: 1) Wetted su rface area (WSA) analysis, 2) Sampling of vessel hull biofouling, 3) Fouling assemblage diversity, abundance and se ttlement in the Columbia River 4) Fouling assemblage viability in a freshwater sy stem.

1) Preliminary results have shown that >42 million m 2 of WSA has arrived into th e Columbia River between 2002 and June 2005. B ulk carriers have provided the majority of this figure with >58%, followed by container ships (13%) and roll on/roll off car carrie rs (11%). Current analysis is focusing on the origin and distance traveled by these vessels to ascertain the primary source regions of Co lumbia River port vessels and associ ated hull fouling biota.

2) Sampling of ships hulls has been divi ded between two sources: dire ct sampling of hulls during dry docking and video analysis of underwater hull surveys carried out by local maritime companies. To date, nine dry docked vessels have been sampled with propor tions of fouling on hulls ranging from <1% to 90%. Vessels analyzed fro m hull video analysis generally had lower levels of fouling (< 1% to 22%), although one vessel that had been out of commission for a pe riod of years had approximately 80% of its hull fouled. The h igh variability recorded from the 22 vessels analyzed thus far is probably a function of different patterns in voyage routes, expos ure to freshwater and hull husbandry schedules. However, this analysis has been primarily qualitative a nd vessels surveyed may not be fully representative of the commercia l fleet entering Lower Columbia River (LCR) ports. Fouling organi sms encountered thus far includ e species of algae, mollusk, bryozoa n, hydroid, cnidarian, polychaete, an d crustacean (including the introduced barnacle Balanus improvisus ). The majority of organisms were not alive upon co llection and a finalized sp ecies list will be made.

3) A preliminary study of rocky substrates near ports revealed very low diversity of foulin g organisms with only ephemeral E

nteromorpha and Cladophora type algal species present. As a resu lt, fouling surveys and settlement pane ls were restricted to areas near the mouth of the river (<40 miles from the m outh) where seawater intrudes to create es tuarine conditions. Fouling panels have b een placed at low tide/immediate subtidal levels for approximately 3 months. To date, analysis of th ree sites (18 panels) has revea led fouling loads have been minimal (<10% panel area c overed). These low levels of settlement o ccurred in sites of both high fouling densit y (rocks dominated by mussels, barnacles and limpets) and low fouling densit y (areas where fouling loads we re characterized by green eph emeral algae and almost no fauna). Afte rthe predetermined submersion time , more panels will be collecte d from boat harbors and other rocky 

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4) Settlement panels have be en deployed at a site of high salinity and f ouling abundance along the Oregon coast (near Tillamook Bay ). These panels will be used in an experiment which will mimic the ch ange in salinity that occurs when ships enter the Columbia Ri ver (salt wedge) system. The aim is to determine the levels of mortality and 'drop off' of random fouli ng assemblages in freshwater.



## Discussion:

The colonizable surface, or wetted surfac e area, of ships' hulls has the potential to inoculate the receiving waters of a port on every voyage. The same is not true of ballast wa ter whereby large quantities of water trans ported to a port are not always released i n that port. Therefore, the underlying potential for invasions to occur via hul l fouling is intrinsically linked to WSA arrivals. Analyses o f ballast water volumes being released into US ports has been conducted (Min ton et al, in press), and one co arse analysis of WSA arrivals to the US revealed that over 400 million m 2 (or 1.5 × the area of Verm ont ) of WSA arrives annually from different bioregions (Miller & Ruiz, in prep).

In the previous 3 1⁄2 years, >42million m 2 WSA has arrived into th e LCR. Fouling levels on vessels sampled have been highly vari able, ranging from >1% to 90% of the wetted surfac e area. Estimates of the commercial fleet in general suggest that even the best mai ntained vessels have between 5% and 20% or their hulls covered in biofouling. A crude estimate would then suggest that, since 2002, bet ween 2.1million and 8.4million m 2 of fouled surface area has entered the system.

However, a major limiting factor for fouling organisms in this syst em is low salinity, which acts as an abrupt barrier to these organisms soon after vessels cross the mouth of the rive r. Further analysis of ships' hull from the LCR and experimental analysis of foul ing assemblages exposed to severe re ductions in salinity will provide further evidence to the extent of the threat that hull foulin g carries in terms of species invasions in the LCR.

Two previous studies regarding hull fouling have involved the LCR. In both, only one ship was examined and it was assumed that no fouling organisms survived after visiting the system. Despite th is, approximately 10% of introduc ed species in the LCR may have arrived via hull fouling and in the context of the larger issue of invasi ons within the system, data is required for any management ste ps that may be required to accurately assess and reduce the threat of the hull fouling vector.



## Further work:

Relative to ballast water research, hull f ouling is poorly studied and the majority of studies have been primarily qualitative. This is partly because vessel hulls are difficult to sample in a standardized way. As a result, basi c knowledge of the extent and composition of biofouling transfers arriving at US ports is unknown. The relative importance of shi pping characteristics such as hull husbandr y, origin, voyage duration, and docking durations are al so unknown. We previously developed a protocol to sample ships hulls, using ROV technology in conjunction with the US Navy Power and Protective Systems (Caderock) division. We plan to undertake multiple deployments of this technology to build a database of many tens of vessels sampled at various Pa cific coast ports. Combined wit h a broader scale and detailed examination of ve ssel (WSA) activity on the west coast, this will provide a baseline of quantitative data from representative ships to determine the threat from the hull fouling vector to US coastal ecoysystems. 

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