Lynn Ficarra

The Use of Benthic Filter Feeders to Mitigate Eutrophication in Coastal

Systems

“an increase in the rate of supply of organic matter to an ecosystem.” (Nixon 1995)

N & Pland clearing, sewage, fertilizer, animals, fossil

fuels, industryPhytoplankton (Paerl 1988, Diaz and Rosenberg 2008)

Block sunDie, sink to bottom, microbial respiration, hypoxia

Eutrophication

Remove phytoplankton, nutrients, organic materials, bacteria, and much much more!

Filter Feeders!

(Ruesink et al. 2005, Gili and Coma 1998, Levinton 1972).

Filtration rate Depends on species, size, water velocity, temperature

Efficiency of particle retentionDepends on filtering structure

(Comeau et al. 2008, Rice 2001, Eastern Oyster Biological Review Team 2007)

Particle Capture

Gills (Riisgard 1988)Parallel filamentsCiliary tracts: create current, capture particles

Particles sorted (Newell 2004)Rejected: pseudofecesDigested: feces

Mucus-coated aggregates Released to benthos

Bivalves

Filtration Rate (Rank)

Retention of Particles >4-

5µm

Retention of 2µm

ParticlesCrassostrea virginica (Eastern oyster)

1 100% 50%

Geukensia demissa (Ribbed mussel)

2 100% 35-75%

Argopecten irradians (Bay scallop)

2 100% 15%

Brachiodontes exustus (Scorched mussel)

3 100% 35-75%

Spisula solidissima (Atlantic surfclam)

3 100% 35-75%

Mercenaria mercenaria (Northern Quahog)

4 100% 35-75%Riisgard 1988

Mussels and eastern oysters performed well in both studies

Crassostrea virginicus and Mytilus edulisNative to east coast of U.S.

Capture Rate (mgC m-

2d-1)Aulacomya ater (mussel) 1787Chlamys islandica (scallop) 3621Crassostrea virginica (oyster)

573

Geukensia demissa (mussel) 30Mercenaria mercenaria (quahog)

351

Ostrea edulis (oyster) 9-30Gili and Coma 1998

Atlantic coast of U.S.0.6-5 m depth20-30°C optimal

Survive freezing and >45°C, feeding rate affectedSurvive at salinities of 5-40 pptFiltration rate up to 30-40 L h-1

Create oyster reefsPromotes biodiversitySubstrate for more suspension feeders

(Ruesink 2005, MacKenzie 1996, Stanley and Sellars 1986, Galtsoff 1964, Shumway 1996, Eastern Oyster Biological Review Team 2007, Pechenik 2005)

Crassostrea virginica (Eastern Oyster)

Coast of Canada to North Carolina1-10 m depth5-20°C optimal

Survive freezing and up to 29°C>18 ppt ideal

Survive low salinities 4-18 ppt, growth slowedFiltration rate 1.34-2.59 L h-1

Mussel bedsIncreases biodiversitySubstrate for more filter feeders

(Zagata et al. 2008, Goulletquer 2012, Bayne and Widdows 1978)

Mytilus edulis (Blue Mussel)

Filtration rates at 9°C (Comeau et al. 2008)M. edulis: 1.82-2.90 L h-1 C. virginica: 0.05-1.21 L h-1

Optimal conditions: C. virginica faster than M. edulis

Cold conditions: M. edulis fasterUse both for eutrophication control

C. virginica vs. M. edulis

Average filtering rate at optimal conditions for 44 filter feeding species is 7.8 L g-1h-1 dry weight (Pomeroy, D’Elia, and Schaffner 2006)

Sponges (Milanese et al. 2003)retain up to 80% suspended particlesCapture small particles that others miss

(bacteria)

Other Filter Feeders

Liverpool (Allen and Hawkins 1993)Mussels introduced to eutrophic water

surrounding docksTwo years later water quality and oxygen levels

in water column and sediments improvedChesapeake Bay (Newell 1988)

Pre-1870: oysters filter bay in 3-6 daysNow: 325 days

Case Studies

Competitive exclusion (Ruesink 2005)

Toxic shellfish (MacKenzie et al. 2004)

Invasive species (Ruesink 2005)Hitchhikers

Pathogens (Moss et al. 2007)Asian oyster, Chesapeake Bay2 protist parasites not found in U.S. watersViruses, cestodes, other protist parasites

Negative Impacts

Refer to Accompanying Paper

References