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Abundance And Distribution Of Planktonic Archaea And Bacteria In The Waters West Of The Antarctic Peninsula, Matthew Church, Edward F. Delong, Hugh Ducklow, Markus Karner, Christian Preston, David M. Karl
Abundance And Distribution Of Planktonic Archaea And Bacteria In The Waters West Of The Antarctic Peninsula, Matthew Church, Edward F. Delong, Hugh Ducklow, Markus Karner, Christian Preston, David M. Karl
VIMS Articles
Polyribonucleotide probes targeting planktonic archaeal (Group I and II) and bacterial rRNA revealed that Archaea comprised a significant fraction of total prokaryote cell abundance in the marine waters west of the Antarctic Peninsula. Determinations of Archaea and Bacteria cell abundances were made during two research cruises to the Palmer Long‐Term Ecological Research region during the austral winter and summer of 1999. During the austral summer, surface water abundances of Group I (GI) Archaea were generally low, averaging 4.7 x 103 cells ml−1 and accounting for 1% of the total picoplankton assemblage. The abundance of GI Archaea increased significantly with depth, …
Grazing And Colony Size Development In Phaeocystis Globosa (Prymnesiophyceae): The Role Of A Chemical Signal, K Tang
VIMS Articles
The bloom-forming prymnesiophyte Phaeocystis globosa forms hollow, spherical, mucilaginous colonies that vary from micrometres to millimetres in size. A recent paper gave the first empirical evidence that colony size increase in P. globosa is a defensive response against grazers, and knowing the signalling mechanism(s) behind this response will thus be a key to understanding the trophodynamics in systems dominated by this species. I conducted experiments with specially designed diffusion incubators, each of which consists of a non-grazing chamber (with P. globosa only) and a grazing chamber (grazers + phytoplankton) connected by 2 mum polycarbonate membrane filters. The results showed that …
Spatial Dynamics And Value Of A Marine Protected Area And Corridor For The Blue Crab Spawning Stock In Chesapeake Bay, Rom Lipcius, Wt Stockhausen, Rochelle D. Seitz, Pj Geer
Spatial Dynamics And Value Of A Marine Protected Area And Corridor For The Blue Crab Spawning Stock In Chesapeake Bay, Rom Lipcius, Wt Stockhausen, Rochelle D. Seitz, Pj Geer
VIMS Articles
In lower Chesapeake Bay, a 172,235 ha marine protected area and corridor (MPAC) was recently established to protect blue crab adult females either en route to or at the spawning grounds during the reproductive period. The MPAC was justified due to a recent substantial decline in spawning stock biomass. It was situated in waters deeper than 10 in throughout the lower bay due to the high abundances of adult females in this zone, and it was an expansion of a historical spawning sanctuary near the bay mouth to include northward extensions (upper and lower MPACs). We examined spatial dynamics of …
Potential Bottom-Up Control Of Blue Crab Distribution At Various Spatial Scales, Rochelle D. Seitz, R. Lipcius, Wt Stockhausen, Et Al
Potential Bottom-Up Control Of Blue Crab Distribution At Various Spatial Scales, Rochelle D. Seitz, R. Lipcius, Wt Stockhausen, Et Al
VIMS Articles
Top-down (i.e., predation), bottom-up (i.e., food availability), and physical factors may influence blue crab (Callinectes sapidus) distribution. To assess the role of bottom-up and physical process in blue crab distributions, we concurrently measured density of the blue crab (Callinectes sapidus), density of its principal prey, the Baltic clam (Macoma balthica), and physical characteristics in mud and sand habitats spanning various spatial scales (1-10 km and 10-50 km) in the York River, Chesapeake Bay. Clam and crab densities were intermediate in mud, low in downriver sand, and high in upriver sand. Clam and crab densities were not correlated in mud. whereas …
Trophic Uptake And Transfer Of Dmsp In Simple Planktonic Food Chains, Kw Tang, R Simo
Trophic Uptake And Transfer Of Dmsp In Simple Planktonic Food Chains, Kw Tang, R Simo
VIMS Articles
Recent field studies suggest that a large portion of phytoplankton-DMSP could be lost to grazing by protozoans, but the fate of the grazed DMSP remains uncertain. In the laboratory we studied trophic uptake and transfer of phytoplankton-DMSP through simple planktonic food chains using 2 experimental approaches: (1) A direct approach measured the ingestion and retention of phytoplankton-DMSP by the heterotrophic dinoflagellate Gyrodinium dominans. Overall, DMSP content of G. dominans estimated by the direct approach was highly variable, likely because of the low G. dominans biomass relative to phytoplankton in the samples. (2) An indirect approach, in which the omnivorous copepod …
Bacterioplankton Dynamics In The York River Estuary: Primary Influence Of Temperature And Freshwater Inputs, G. E. Schultz, E. D. White, H. W. Ducklow
Bacterioplankton Dynamics In The York River Estuary: Primary Influence Of Temperature And Freshwater Inputs, G. E. Schultz, E. D. White, H. W. Ducklow
VIMS Articles
Bacterial community dynamics were investigated over seasonal and basin scales within the York River estuary, Virginia. Variables describing bacterioplankton dynamics were measured at 6 stations spanning the entire salinity gradient (0 to ca. 20 psu over 60 km). Samples were collected monthly from June 1996 through May 1997 and every other month from June 1997 through May 1998. Bacterial abundance and production were high throughout the estuary. Bacterial abundance ranged from 4.4 x 10(8) to 1.3 x 10(10) cells l(-1). Incorporation of (3)H-thymidine ranged from 10 to 863 pmol(-1) h(-1) while (3)H-leucine incorporation rates ranged from 25 to 1963 pmol …
Seed-Density Effects On Germination And Initial Seedling Establishment In Eelgrass Zostera Marina In The Chesapeake Bay Region, R J. Orth, Jr Fishman, Mc Harwell, Sr Marion
Seed-Density Effects On Germination And Initial Seedling Establishment In Eelgrass Zostera Marina In The Chesapeake Bay Region, R J. Orth, Jr Fishman, Mc Harwell, Sr Marion
VIMS Articles
The influence of Zostera marina L. seed-density on germination and initial seedling success was investigated using seed-addition field experiments at 2 scales in the Chesapeake Bay region in 1999 and 2000. We first tested whether germination rates and initial seedling establishment were affected by initial seed-densities of 2.5, 25, 250, and 1250 seeds m(-2) within 4 m(2) plots. We then tested whether plot size affects germination rates, following the hypothesis that rates of seed predation might be different in large and small plots. We broadcast seeds at a single density (500 seeds m(-2)) but at a much larger plot size …
Microbial Mediation Of 'Reactive' Nitrogen Transformations In A Temperate Lagoon, Iris C. Anderson, Kj Mcglathery, Ac Tyler
Microbial Mediation Of 'Reactive' Nitrogen Transformations In A Temperate Lagoon, Iris C. Anderson, Kj Mcglathery, Ac Tyler
VIMS Articles
Coastal lagoons positioned along the land margin may play an important role in removing or transforming 'reactive' nitrogen during its transport from land to the ocean. Hog Island Bay is a shallow, coastal lagoon located on the ocean-side of the Delmarva Peninsula in Virginia (USA). External nitrogen inputs are derived primarily from agriculturally enriched groundwater, and these support, in part, the high production of benthic macroalgae and microalgae as the dominant primary producers. This study focuses on processes in the water column (phytoplankton and bacterial) and in the sediments (microalgal and bacterial) responsible for transformations of dissolved inorganic and organic …
Critical Evaluation Of The Nursery Role Hypothesis For Seagrass Meadows, Kl Heck, G Hays, R J. Orth
Critical Evaluation Of The Nursery Role Hypothesis For Seagrass Meadows, Kl Heck, G Hays, R J. Orth
VIMS Articles
The vast majority of published papers concerning seagrass meadows contain statements to the effect that seagrass beds serve as important nurseries for many species. We reviewed more than 200 papers that were relevant to the nursery role hypothesis. We used both vote counting and meta-analytic techniques to evaluate whether the body of previous studies that report seagrass meadows to be nursery grounds actually contain data that support this proposition. We restricted our analyses to papers that compared seagrass beds to other habitats, and examined data on a variety of well-studied species concerning their density, growth, survival and migration to adult …
Substrate Selection By Blue Crab Callinectes Sapidus Megalopae And First Juvenile Instars, J Van Montfrans, Ch Ryer, R J. Orth
Substrate Selection By Blue Crab Callinectes Sapidus Megalopae And First Juvenile Instars, J Van Montfrans, Ch Ryer, R J. Orth
VIMS Articles
Various marine and estuarine species utilize chemical cues during settlement. We investigated responses by megalopae and first juvenile (J1) blue crabs to common Chesapeake Bay substrates in mesocosm and field experiments. Mesocosm trials examined responses of megalopae or J1 crabs to sand, marsh mud, live oysters Crassostrea virginica, sun-bleached oyster shell, eel grass Zostera marina and artificial seagrass in replicate 160 l tanks. Either 10 megalopae or J1 crabs isolated in each of 6 substrates were allowed total access after acclimation to test the null hypothesis of equal distribution among substrates after 13 h. Thirty-five percent of megalopae were recovered …
Effects Of Hypoxia On Predator-Prey Dynamics Of The Blue Crab Callinectes Sapidus And The Baltic Clam Macoma Balthica In Chesapeake Bay, Rochelle D. Seitz, Ls Marshall, Ah Hines, Kl Clark
Effects Of Hypoxia On Predator-Prey Dynamics Of The Blue Crab Callinectes Sapidus And The Baltic Clam Macoma Balthica In Chesapeake Bay, Rochelle D. Seitz, Ls Marshall, Ah Hines, Kl Clark
VIMS Articles
In general, hypoxia (< 2 mg O-2 l(-1)) is detrimental to marine food webs because of faunal declines associated with persistent, severely low oxygen. However, transfer of benthic production to higher trophic levels could be facilitated under hypoxia if infauna migrate to shallower burial depths, increasing their availability to predators. A series of outdoor mesocosm and laboratory experiments were conducted in 3 years (1999 to 200 1) to quantify the effects of hypoxia upon (1) predation by the blue crab Callinectes sapidus on the Baltic clam Macoma balthica, a biomass dominant in Chesapeake Bay, and (2) burial depth and survival of M, balthica. For the predation experiments, 12 M. balthica were transplanted into replicate 1200 1 mesocosms at 48 clams m(-2) under normoxia (>8 mg O-2 l(-1)) or low dissolved oxygen (low DO; l(-1)) either without or with a male blue crab that was allowed 2 d to feed upon the clams. Predation-induced proportional mortality of clams was significantly lower under low DO than under normoxia in all 3 years. Thus, under short-term hypoxia, both crab feeding efficiency and trophic transfer from M balthica to blue crabs were reduced. Changes in clam burial depth due to oxygen levels was determined by establishing normoxic and low DO treatments in replicate 208 1 aquaria in 2 years. Burial depth after exposure …