Shannon L. Meseck

Effect of ocean acidification on growth and otolith condition of juvenile scup, Stenotomus chrysops

Abstract Increasing amounts of atmospheric carbon dioxide (CO2) from human industrial activities are causing changes in global ocean carbonate chemistry, resulting in a reduction in pH, a process termed “ocean acidification.” It is important to determine which species are sensitive to elevated levels of CO2 because of potential impacts to ecosystems, marine resources, biodiversity, food webs, populations, and effects on economies. Previous studies with marine fish have documented that exposure to elevated levels of CO2 caused increased growth and larger otoliths in some species. This study was conducted to determine whether the elevated partial pressure of CO2 (pCO2) would have an effect on growth, otolith (ear bone) condition, survival, or the skeleton of juvenile scup, Stenotomus chrysops, a species that supports both important commercial and recreational fisheries. Elevated levels of pCO2 (1200–2600 μatm) had no statistically significant effect on growth, survival, or otolith condition after 8 weeks of rearing. Field data show that in Long Island Sound, where scup spawn, in situ levels of pCO2 are already at levels ranging from 689 to 1828 μatm due to primary productivity, microbial activity, and anthropogenic inputs. These results demonstrate that ocean acidification is not likely to cause adverse effects on the growth and survivability of every species of marine fish. X‐ray analysis of the fish revealed a slightly higher incidence of hyperossification in the vertebrae of a few scup from the highest treatments compared to fish from the control treatments. Our results show that juvenile scup are tolerant to increases in seawater pCO2, possibly due to conditions this species encounters in their naturally variable environment and their well‐developed pH control mechanisms.

Temporal Variability in Phytoplankton Removal by a Commercial, Suspended Eastern Oyster Nursery and Effects on Local Plankton Dynamics

ABSTRACT Quantitative measurements of phytoplankton removal in a natural setting are needed to evaluate interactions between aquacultured bivalve populations and the surrounding environment. We report high-frequency (15-min) measurements of environmental variables relevant to oyster feeding and excretion at the inflow and outflow of an oyster nursery—floating upweller system (FLUPSY)—from June through September 2010 in the East Creek embayment, Peconic Estuary, NY. We demonstrated large variability in oyster particle clearance rate on short- (minutes to hours) to long-term (seasonal) timescales, including oyster responses to environmental variation, such as diurnal temperature and dissolved oxygen cycles, wind-driven turbulence, and the presence of harmful algae. A diel cycle in clearance rates calculated from whole FLUPSY measurements was apparent, with a maximum weight-specific clearance rate (CRW) of 2.21 L/h/g occurring around midnight, and a minimum CRW of 0.32 L/h/g at 0740 HR, coincident with the lowest concentration of dissolved oxygen in the water. Throughout the season, oyster growth and feeding showed constant, high values from June 12 to July 21, with a median CRW of 0.95 L/h/g. From late July to September, a toxic dinoflagellate, Cochlodinium polykrikoides, was present frequently in the water, and was coincident with depressed oyster feeding, slow/no growth, and increased mortality. Overall, the FLUPSY in East Creek did not have a large impact on the abundance of phytoplankton in the water. Future modeling efforts projecting carrying capacity and ecosystem services of shellfish aquaculture and restoration need to take into account the potential for temporal variability in feeding resulting from environmental variation, as observed in this study.

Nutrient interactions between phytoplankton and bacterioplankton under different carbon dioxide regimes

Light, nutrients, temperature, pH, and salinity are important factors in controlling the growth of phytoplankton and bacterioplankton. Supply of key nutrients to these communities can result in mutualistic or competitive relationships between bacterioplankton and phytoplankton. In this study, we investigated growth and uptake of nutrients by the marine prasinophyte flagellate Tetraselmis chui (strain PLY429) in the presence and absence of a community of bacterioplankton at two pH levels. Growth of PLY429 and total nutrient uptake were calculated for each treatment. The addition of bacterioplankton resulted in lower growth rates of PLY429, but the removal of ammonium was greater in those cultures with bacterioplankton present. The division rate of PLY429 was affected by pH; however, pH changes did not result in different uptake rates of nitrate, ammonium, or phosphate by the mixed algal and bacterial assemblage. These findings suggest that bacterioplankton and phytoplankton were competing for ammonium and that a lower pH resulted in more rapid algal growth.

IMPACTS OF A CYANOBACTERIUM CONTAMINATING LARGE-SCALE AQUACULTURE FEED CULTURES OF TETRASELMIS CHUI ON SURVIVAL AND GROWTH OF BAY SCALLOPS, ARGOPECTEN IRRADIANS IRRADIANS

Abstract Large-scale, open, microalgal feed cultures for hatchery and nursery production of marine invertebrates inevitably becomes contaminated with various microbes that can affect productivity and usability of the harvested biomass. In the Greenhouse for Research on Algal Mass Production Systems (GRAMPS) at the NMFS Laboratory in Milford, CT, cultures of Tetraselmis chui (PLY429) often become contaminated with a cyanobacterium; preliminary observations suggested that juvenile bay scallops, Argopecten irradians irradians showed reduced performance when the feed culture became contaminated with this cyanobacterium. We isolated a cyanobacterium from a contaminated culture of PLY429 and conducted a feeding study to determine if this isolate affects survival and growth of juvenile bay scallops, either alone or in combination with PLY429, thereby simulating feeding of a contaminated culture. Bay scallops were given a diet of either 100% PLY429, 50% PLY429 with 50% cyanobacteria, 100% cyanobacteria, or starved. There was 100% mortality of bay scallops by week 3 when they were starved, with a significant difference in survival between diets (P < 0.01). At 6 wk the scallops fed only the cyanobacterium had 63% survival, 93% survived in the mixed diet, and 98% survived when fed 100% PLY429. The net growth of bay scallops on the different diets was also significantly different (P < 0.01) with scallops fed 100% PLY429 having the highest shell-growth rate of 198-μm scallop−1 d−1, and growth rates of 82-μm scallop−1 d−1 on the mixed diet, and 65-μm scallop−1 d−1 for the cyanobacterial diet. These findings suggest that the cyanobacterium will not cause instant mortality, but it will not support sustained survival and growth over time scales of weeks.

Benthic Ecology of Northern Quahog Beds with Different Hydraulic Dredging Histories in Long Island Sound

ABSTRACT Mercaldo-Allen, R.; Goldberg, R.; Clark, P.; Kuropat, C.; Meseck, S.L., and Rose, J.M., 2016. Benthic ecology of northern quahog beds with different hydraulic dredging histories in Long Island Sound. This paper evaluates benthic community composition of four shellfish beds in Long Island Sound near Milford, Connecticut, where northern quahog or hard clams, Mercenaria mercenaria (Linnaeus 1758), were harvested by hydraulic dredge. These leased beds reflect a variety of dredging histories; 0 year (dredged just before sampling began), 1 year postharvest, 2 years postharvest, and an inactive clam bed left fallow for at least 10 years. Benthic sediment was sampled at 1- to 2-week intervals from June to October 2011 using a Smith–McIntyre grab. Benthic community composition was significantly influenced by dredging history and sampling month. Abundance of benthic organisms (number of individuals and biovolume) and total organic matter concentrations were significantly greater at the 0-year site than at the 1-, 2-, and 10+-year sites, and significantly greater at the 1- and 2-year sites than at the 10+-site. Newly settled bivalves, primarily Nucula spp. and Yoldia limulata, were significantly more prevalent on the recently harvested 0-, 1-, and 2-year sites vs. the 10+-year site and highest at the 0-year site. A significantly greater number of species was observed on the 1- and 2-year sites vs. the 0- and 10+-year locations. Species richness at the 0-year site was significantly lower than at the 1-, 2-, and 10+-year sites, whereas diversity and evenness at the 0-year site was significantly lower than at the 10+-year site. This study observed successional changes in community structure of inshore clam beds related to the length of time elapsed after harvest dredging.