Principal Investigator
Project Goal:
The goal of this project is to determine species composition, habitat use, and changes over time for organisms that live in the various types of sediment in the Rhode River.
Infaunal Benthic Invertebrate Organisms
"Infaunal" refers to aquatic animals that live in the substrate of a body of water and which are especially common in soft sediments. "Benthic" refers to anything occurring at or in the bottom of a body of water. "Infauna" are the creatures tht live in the sediments.
In the Chesapeake Bay, benthic infauna such as clams, snails, polychaetes, flatworms, and small crustaceans, are abundant and crucial to a healthy ecosystem.
They help to filter water, recycle organic matter, and are important forage (prey) for fish, reptiles, amphibians, and larger crustaceans (such as blue crabs and horseshoe crabs). Many of the organisms found in the benthos are suspension feeders and deposit feeders. Suspension feeders, also known as "filter feeders", process particles floating in the water column. Deposit feeders consume organic matter lying on or in the sediment.
Seasonal fluctuations of species and their abundances can be driven by recruitment (addition of individuals to a population), predation, poor habitat conditions (such as low dissolved oxygen), human impacts like shoreline hardening and meteorological events like hurricanes.
Benthic Infauna in the Rhode River
The Rhode River is a representative tributary of the Chesapeake Bay. Macroinvertebrates, such as crustaceans, worms, and mollusks comprise the Rhode River's soft bottom community. They live in or on the bottom of the river in mud, sand, clay, marsh detritus, leaf litter, or combinations of these sediment types. Infaunal species are responsible for significant interactions within the benthic environment which in turn, impact the biodiversity and functional processes within the entire estuarine ecosystem. Long-term data on these species gives us 1) information on the species composition and fluctuating abundances of these organisms over time and in differing habitats and 2) a better understanding of the processes that regulate their community and population dynamics. Such dynamics include predator-prey interactions, recruitment, habitat use and responses to environmental factors such as salinity, temperature, and dissolved oxygen. Integrating benthic infaunal data with our other long term sampling programs provides insight into processes structuring ecosystem interactions within the Rhode River
As part of a complex food web, infaunal communities are composed of both predators and prey. Trophic level (positions in the food web) of these species may change during its life cycles as the organism grows and their size, feeding mechanism, and nutritional requirements change.
Processes such as bioturbation (sediment disturbance) is caused by infaunal burrowing and feeding, especially by deposit feeder species such as worms or certain species of clams. Bioturbation can, among other things, affect oxygen levels in sediments, cause redistribution and decomposition of organic matter, and alter the amount of suspended particles in the water. This, in turn, may negatively or positively affect water quality, refuge patterns, and feeding behavior of organisms.
Sampling Benthos in the Rhode River
Our lab has been tracking variation of benthic species composition and abundance with seasonal sampling since 1979. We have five sites in the Rhode River where we sample for benthic organisms. Two sites have sand substrate and three have mud. We take seven core samples per site. Samples are taken four to eight times a year. Sediment core samples are taken with a pipe core sampling device that is either attached to the end of a pole (mud stations) or operated by a SCUBA diver (sand stations). The pipe core collects a core sample that is 35 cm deep. All core samples are then sieved on a 500 μm mesh screen to remove smaller particles of the sand/mud. Animals >500 μm are preserved and stained to be processed later in the lab.
In the lab, the organisms are sorted, counted, and identified to the species level under a dissecting microscope. Mollusks are measured. All data are recorded and entered into a database for analysis.
Sixty benthic species have been identified in the Rhode River's soft bottom sediment of sand and mud.
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