Marine Life Colonization of Experimental Reef Habitat (1/5)
Marine life colonization of experimental reef habitat
in temperate ocean waters off New Jersey, 1996-2004
This investigation was partially funded by the Federal Aid to Sportfish Restoration Program
for the original paper, see here.
ABSTRACT
A biological colonization study of experimental reef habitats in temperate ocean waters off New Jersey was conducted over a 96-month period. A total of 145 different taxa of 9 phyla were identified within the experimental units, including 42 arthropoda, 37 annelida and 43 molluska. Individual organisms had an estimated mean abundance of 534,566 organisms/m2 of habitat footprint, including 105 fish, 4,639 crabs and 14 lobsters. Colonial organisms covered 87,554 cm2 of the habitat surface area. Mean total biomass of the organisms inhabiting the units was 84,175 g/m2, with blue mussel comprising 63 percent of the total. The carrying capacity of the experimental habitat for all species of marine life was about 152,801 g/m2. Predation accounted for an 80 percent reduction of biomass between surfaces exposed and not exposed to predators. There were no statistically significant differences in biological colonization rates of sessile epibenthos on concrete, rock, steel and rubber substrates. On an equivalent area basis, the biomass enhancement ratios of the experimental reef habitats over surf clam-dominated and polychaete/crustacean-dominated sand bottom habitats ranged from 35 to 1,124 and 2,773 to 3,200 times, respectively. A simplified, three-tiered reef habitat food chain consisted of 84.5 percent sessile/sedentary invertebrates, 11.0 percent mobile invertebrates and 4.5 percent juvenile and adult fish. The results suggest that complex reef habitats provide both attachment surfaces and refuge habitats that support a diverse and abundant marine life community.
ACKNOWLEDGMENTS
The Ocean County Bridge Department transported the experimental habitats to the Barnegat Light Reef Site. The U.S. Environmental Protection Agency dive team retrieved a habitat during the first year of the study. Roger Hoden and George Dreher retrieved habitats in subsequent years. Linda Barry assisted in field collection and performed laboratory and data analysis. Frank Steimle, National Marine Fisheries Service, assisted in field collections and identifications and reviewed the manuscript. Jeff Carlson, Barry Preim and Stacey Reap assisted in habitat fabrication, habitat retrieval or laboratory analysis. Statistical analyses were performed by Deborah Vareha. Barry Preim prepared the graphics. Mary Anne Lyons and Tricia Mahoney typed the manuscript. This investigation was partially funded by the Federal Aid to Sportfish Restoration Program.
INTRODUCTION
An inventory of the biological attributes of marine life communities inhabiting reefs, including species diversity, biomass, life stages, predation level, habitat preferences, and succession, is an essential ingredient of any reef-building program. Biological monitoring is especially important in assessing the effectiveness of New Jersey's reef program in meeting its primary objective of providing habitat for fish and invertebrates (NMFS 1995).
While most artificial reefs are built for economically important fish, food and game shellfish (lobsters, oysters) and/or fishermen and divers, the epifaunal invertebrate community is an important ecological component of the reef community, providing the basis of the food chain that supports harvestable resources and comprising the vast majority of life, by numbers and biomass, inhabiting ocean reefs. The intention of this investigation was to inventory the smaller, mobile and sessile invertebrate communities and juvenile fish inhabiting New Jersey reefs. No attempt was made to examine adult fish populations.
Turf or fouling communities, composed of sessile, invertebrate epifauna and algae, in shallower waters, are inventoried in a variety of ways. Palmer-Zwahlen and Aseline (1994) used divers to identify fouling organisms found within randomly selected quadrants. Feigenbaum et al. (1985) and Foster et al. (1994) had divers scrape reef surfaces and collect samples for laboratory analysis. Wendt et al. (1989) combined scrape samples with underwater photographs to inventory turf communities. Many researchers have placed settlement plates of various reef-building materials on sea floor racks that can later be retrieved by divers for laboratory analysis (Sheehy 1983; Woodhead and Jacobson 1985; Bailey-Brock 1989; Hawkins 1995; Tumbiolo et al. 1995; Chang and Pearce 1995).
The collection of cryptic or mobile epifauna, which includes crabs, shrimps, worms, snails, starfish and small juvenile fish, is more challenging since these animals are small, cryptic and often hide in holes and crevices in reef structures or among sessile epifaunal growth. Benson (1989) used a suction device to capture mobile prey in turf scrape samples. Traps and nylon bags are also used to capture certain mobile invertebrates (Forrest Blau and Byersdorfer 1994). The shortcoming of using traps is that they do not provide information regarding the numbers of mobile invertebrates per unit of habitat. In clear, tropical waters, the common method of evaluating juvenile fish populations is through counts by divers (Gorham and Alevizon 1989; Danner et al. 1994; Jessee et al. 1985; Adams 1993; Bohnsack et al. 1997; Brock and Kam 1991).
The use of divers to observe mobile epifauna and juvenile fish and to quantify their population size underwater on New Jersey reefs is impractical because of poor visibility, and the cryptic habits or large population numbers of many of the species. Another factor that prohibits using diver observations to collect biological information is the vast amount of field time that is needed to accomplish the task. For these reasons, we decided to use specially designed, miniature reef habitats as experimental sampling units that could be placed on the sea floor and later retrieved by divers, disassembled, and samples returned to the lab for analysis. The experimental habitats were designed to afford extensive colonization surfaces for sessile epifauna, including 8 settlement plates of 4 common reef-building substrates, numerous and varied hiding spaces for mobile epifauna and an internal chamber for juvenile fish. Thus, all of the components of the reef community that we were investigating could be collected simultaneously in a few hours and brought back to the lab where a thorough, detailed analysis could be completed.
According to Seaman (2000), our study was designed to obtain first-level information about temperate reef biology - species diversity, abundance, biomass, size ranges and predation pressure. Specifically, the objectives of this reef performance monitoring survey included:
- an inventory of the sessile and mobile epifauna and juvenile fish inhabiting an experimental reef habitat;
- a quantification of the standing stock biomass of sessile and mobile invertebrate epifauna and juvenile fish per unit of habitat volume on an experimental reef habitat;
- an examination of the successional changes in species diversity and standing stock biomass of epifaunal invertebrates on an experimental reef habitat over time;
- a comparison of the colonization rates of sessile invertebrate epifauna on 4 different reef-building substrates;
- an investigation of predation pressure on sessile invertebrate epifauna on 4 different reef-building substrates.
