The Growth of Estuarine Resources (Zostera marina, Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians, Cyprinodon variegatus) in Response to Nutrient Loading and Enhanced Suspension Feeding by Adult Shellfish

Abstract

While many coastal ecosystems previously supported high densities of seagrass and abundant bivalves, the impacts of overfishing, eutrophication, harmful algal blooms, and habitat loss have collectively contributed to the decline of these important resources. Despite improvements in wastewater treatment in some watersheds and subsequent reduced nutrient loading to neighboring estuaries, seagrass and bivalve populations in these locations have generally not recovered. We performed three mesocosm experiments to simultaneously examine the contrasting effects of nutrient loading and historic suspensionfeeding bivalve densities on the growth of eelgrass (Zostera marina), juvenile bivalves (northern quahogs, Mercenaria mercenaria; eastern oysters, Crassostrea virginica; and bay scallops, Argopecten irradians), and juvenile planktivorous fish (sheepshead minnow, Cyprinodon variegatus). High nutrient loading rates led to significantly higher phytoplankton (chlorophyll a) levels in all experiments, significantly increased growth of juvenile bivalves relative to controls with lower nutrient loading rates in two experiments, and significantly reduced the growth of eelgrass in one experiment. The filtration provided by adult suspension feeders (M. mercenaria and C. virginica) significantly decreased phytoplankton levels in all experiments, significantly increased light penetration and the growth of eelgrass in one experiment, and significantly decreased the growth of juvenile bivalves and fish in two experiments, all relative to controls with no filtration from adult suspension feeders. These results demonstrate that an appropriate level of nutrient loading can have a positive effect on some estuarine resources and that bivalve filtration can mediate the effects of nutrient loading to the benefit or detriment of different estuarine resources. Future ecosystem-based approaches will need to simultaneously account for anthropogenic nutrient loading and bivalve restoration to successfully manage estuarine resources.

Large Shifts in Commercial Landings of Estuarine and Bay Bivalve Mollusks in Northeastern United States after 1980 with Assessment of Causes

“…Kroncke et al (1998) believe that climate variability may have a larger effect on benthic ecosystems than eutrophication and some other possible factors, but Paerl (2006) suggests it has been difficult to distinguish between these two effects. Nitrogen enrichment does lead to increases in shell growth and soft tissues in quahogs, softshell clams, and bay scallops (Carmichael et al, 2004;Wall et al, 2011Wall et al, , 2013. Anoxia can occur when phytoplankton blooms die in eutrophic waters, killing larvae and postset bivalves.…”

Biodeposition, respiration, and excretion rates of an introduced clam Mercenaria mercenaria in ponds with implications for potential competition with the native clam Meretrix meretrix in Shuangtaizi estuary, China

“…Several studies have concentrated on the seeding breeding, cultivation, and growth performance of M. mercenaria (Weiss et al, 2002;Zhang et al, 2003;Chung et al, 2007;Weiss et al, 2007;Zarnoch and Schreibman, 2008;Arnold et al, 2009;Wall et al, 2011Wall et al, , 2013, but only a few have investigated its physiological ecology (Sma and Baggaley, 1976;Grizzle et al, 2001;Wen et al, 2004;Parent et al, 2008). In addition, suspension-feeding bivalves are well known for their active biodeposition capacity.…”

Sustainable Seagrass Restoration in the Virginia Coastal Bays

“…Many models have tried to explain the relationship between the light attenuation coefficient and water quality , Dennison et al 1993, Wall et al 2011. Dennison et al (1993) found the minimum water quality characteristics using water column chlorophyll a (15 μg/L), total suspended solids (15 mg/L), dissolved inorganic nitrogen (DIN) (10 μM) and dissolved inorganic phosphorous (DIP) (0.67 μM) to sustain submerged aquatic vegetation (SAV) in the Chesapeake Bay and its tributaries.…”

“…Many studies use plant productivity as a way to quantify photosynthetic stress (Peterson and Heck 2001, Carroll et al 2008, Wall et al 2011, Skinner et al 2013). Peterson and Heck (2001) used productivity to quantify positive interactions between Thalassia testudinum and bivalves and found that the presence of mussels at densities greater than 500 m -2 reduced epiphytic loads on leaves and resulted in increased productivity.…”