Feature Story                                                                   July 2012 

Unwanted Species: The Fouling Community

By Monaca Noble

The frilled anemone Metridium Senile growing on a dock in Ketchikan, AK. Photo by Monaca Noble

Have you ever laid on the dock and looked at all of the creatures living just beneath the water? In many parts of the world the community of organisms that live on docks and pilings can be very colorful, diverse and beautiful. But in other areas the organisms are brown, grey, and drab; more fitting of the term used to describe them - fouling. Fouling refers to unwanted material on solid surfaces that impair function; biofouling then, is the unwanted growth of microorganisms, plants, algae, or animals on wetted structures.  

Though the terms fouling and biofouling denote something that is often unwanted, many species that attach to docks, pilings, and boat hulls are also found in natural areas, such as along rocky shores, and play an important role in the health of the environment. They are filter feeders that help clean particulates from the water improving water clarity. They provide nursery habitat for larval fish and crabs, and they are an important source of food for many species including humans. Mussels for example are part of the fouling community.

Species that settle on docks and pilings also settle on the hulls of boats and ships. As the boats move among ports, so too do the organisms attached to their hulls. The fouling organisms attached to the boat hulls can be introduced to new geographic areas when the attached adults spawn and produce larvae that settle on the docks and pilings of a marina or port. For this reason ports and marinas are particularly susceptible to being colonized by invading species from around the world. Introduced species can displace native species and can cause problems for the port, marina, and boat owners tasked with removing them, but also for people in the aquaculture industry located nearby. Many fouling species, such as the rapidly growing colonial tunicate Didemnum vexillum, can overgrow shellfish and equipment causing significant economic damage.

Stacey Havard pulls up a survey plate from a marina in Tampa, Florida. Photo by Michele Repetto. 
Scientists from the Smithsonian Environmental Research Center’s (SERC) Marine Invasions lab, led by Dr. Gregory Ruiz, have been studying the fouling community since 1994, conducting surveys to document both native and introduced species. Over the years, detailed surveys have been conducted in most of the major bays on the US East, West, and Gulfs coasts and Hawaii, Alaska, and Puerto Rico, as while as Australia, Canada, Belize, and Panama (see the map). SERC researchers survey fouling communities by hanging settling plates from docks and pilings and allowing species to settle and grow throughout a three month period during the spring or summer. A settling plate is a PVC (Polyvinyl chloride) panel that is attached to a brick for weight and hung off a dock. The surveys provide information about the diversity and type of species present during a given year as well and information about their relative abundance. More importantly, they allow us to detect and monitor introduced fouling species. Several newly introduced species were discovered during these surveys. For example, the Hydrozoan Moerisia lyonsi was discovered during a 1995 survey of Baltimore Harbor and the Kamptozoan Barentsia benedeni was discovered for the first time in Chesapeake Bay during a 1994 fouling survey. 

Very often we only have the resources to conduct surveys for a single year, but we have been able recently to repeat surveys in multiple years for Valdez, AK, San Francisco Bay, CA, Chesapeake Bay, VA and Tampa Bay, FL. These multiple year surveys begin to assess changes in the fouling community and detect newly introduced species over time. For example, the introduced tunicate Ciona intestinalis has become extremely abundant in San Francisco Bay, whereas the introduced mussel Perna viridis was abundant 10 years ago in Tampa Bay but its population density has dropped significantly since then.

These surveys, combined with intensive analyses to identify and determine the native/introduced status of each of the species found, are being used to create the National Estuarine and Marine Exotic Species Information System (NEMESIS). NEMESIS is being made accessible as an online resource to provide detailed information on approximately 500 introduced marine and estuarine species of invertebrates and algae with established populations in the continental United States. Over time, the survey results and specific location data are being incorporated into NEMESIS and are being used to evaluate nationwide status and trends of coastal marine invasions in the continental US.

The bays and estuaries in which fouling surveys have been conducted, the red suns indicate the sites that were surveyed over multiple years.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   
Survey plates from Tampa, Florida showing the fouling community after three months of growth. Can you find the tunicates, hydrozoan, and green mussel Perna viridis? Photos by Michele Repetto