Lower Rappahannock River Research Articles

Correction: Modeling the Effect of Hypoxia on Macrobenthos Production in the Lower Rappahannock River, Chesapeake Bay, USA

Correction: Modeling the Effect of Hypoxia on Macrobenthos Production in the Lower Rappahannock River, Chesapeake Bay, USA

Effects of seasonal hypoxia on macrobenthic production and function in the Rappahannock River, Virginia, USA

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 490:53-68 (2013) - DOI: https://doi.org/10.3354/meps10470 Effects of seasonal hypoxia on macrobenthic production and function in the Rappahannock River, Virginia, USA S. Kersey Sturdivant1,*, Rochelle D. Seitz2, Robert J. Diaz2 1Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University, 135 Duke Marine Lab Rd., Beaufort, North Carolina 28516, USA 2Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Pt., Virginia 23062, USA *Email: kersey.sturdivant@duke.edu ABSTRACT: Since colonial times, anthropogenic effects have eroded Chesapeake Bay’s health, resulting in an increase in the extent and severity of hypoxia (≤2 mg O2 l-1), adversely affecting community structure and secondary production of macrobenthos in the Bay and its tributaries. The influence of hypoxia on macrobenthic communities is well documented, but less well known is the regulatory effect of hypoxia on macrobenthic production. Changes in macrobenthic production were assessed in the lower Rappahannock River, a sub-estuary of Chesapeake Bay, in an area known to experience seasonal hypoxia. During the spring, summer, fall, and following spring of 2007 and 2008, 10 samples were collected each season for a total of 80 samples, and macrobenthic production was estimated using Edgar’s allometric equation. Additionally, from early spring to late fall, dissolved oxygen concentrations were measured continuously at 2 of the 10 sites in 2007, and 2 of the 10 sites in 2008; in conjunction, the macrobenthic community was assessed through bi-weekly grab samples at these sites. Hypoxic sites had as much as 85% lower macrobenthic production compared to normoxic sites, and macrobenthic production at hypoxic sites was associated with primarily smaller, disturbance-related annelids. Macrobenthic production differed across seasons, and estimated sediment reworking rates were significantly higher during normoxia, indicating that the functional role of the macrobenthic community changed during hypoxia. KEY WORDS: Oxygen depletion · Secondary production · Chesapeake Bay · Macrobenthos · Energy flow Full text in pdf format PreviousNextCite this article as: Sturdivant SK, Seitz RD, Diaz RJ (2013) Effects of seasonal hypoxia on macrobenthic production and function in the Rappahannock River, Virginia, USA. Mar Ecol Prog Ser 490:53-68. https://doi.org/10.3354/meps10470 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 490. Online publication date: September 17, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Long-term trends in the macrobenthos and water quality of the lower Chesapeake Bay (1985–1991)

Long-term trends in macrobenthic communities of the lower Chesapeake Bay, USA, were examined using data collected quarterly (March, June, September and December) from 1985 to 1991 at 16 stations along a salinity gradient from tidal freshwater regions of the major tributaries (James, York and Rappahannock rivers) to the polyhaline region of the main-stem of Chesapeake Bay. A non-parametric trend analysis procedure was applied to five parameters characterizing macrobenthic community structure: community biomass, species richness, abundance of individuals, proportion of biomass composed of opportunistic species (opportunistic biomass composition) and proportion of biomass composed of equilibrium species (equilibrium biomass composition). For the parameters tested 36 trends were detected. For community biomass, five trends were significant; all had positive slopes and occurred in the James and York rivers. For species richness, six trends were significant; all had positive slopes with three trends in the James River, two trends in the York River and one trend in the main-stem of Chesapeake Bay. For abundance of individuals, 17 trends were detected; all abundance trends were seasonally dependent, had positive slopes and occurred at 12 of the 16 stations. For opportunistic biomass composition, four trends were significant; all had positive slopes with one trend in the lower Rappahannock River and three trends in the main-stem of Chesapeake Bay. For equilibrium biomass composition four trends were significant; two trends had positive slopes (one in the James River and one in the York River) and two trends had negative slopes (one in the Rappahannock River and one in the main-stem of Chesapeake Bay). Trends in the James and York rivers were considered to indicate improving conditions for the benthos, while trends in the lower Rappahannock River and the main-stem of the Chesapeake Bay were considered to indicate deteriorating conditions. Deteriorating conditions for the benthos were associated with regions exposed to summer, low dissolved oxygen events. The trends in the indicators of benthic biological community health were inferentially related to trends observed in water quality conditions in the tributaries and main-stem of Chesapeake Bay. All major water quality and biotic trends appeared to correspond in an ecologically meaningful manner.

Effects of hypoxia on estuarine benthos: the lower Rappahannock River (Chesapeake Bay), a case study

The effects of seasonal hypoxia on population dynamics of macrobenthic organisms were studied at a meso-polyhaline, deep sandy-mud habitat in the lower Rappahannock River, a tributary of Chesapeake Bay (Virginia, U.S.A.). Water quality was monitored on a monthly to weekly basis, spring to autumn, to determine the extent, intensity and duration of hypoxic events. Core samples collected along a five-station transect were used to identify species, discern patterns of spatial and temporal variation of abundance, and determine vertical distribution patterns in the sediment relative to dissolved oxygen fluctuations. A significant decrease in macrobenthic abundance followed by defaunation at some stations was attributed to intermittent hypoxia. Abundance and species number were low during summer, decreasing with increasing water depth and upriver direction in relation to lowest dissolved oxygen concentrations. Species composition appeared to be influenced by hypoxia. Annelid polychaetes comprised the largest percentage of the population, with dominance of ‘opportunists’. The magnitude of the responses to hypoxia appeared to be species-specific. Some polychaetous species such as the spionid Streblospio benedicti and the capitellid Mediomastus ambiseta became locally extinct with the onset of severe hypoxia. In contrast, the terebellid Loimia medusa and the spionid Paraprionospio pinnata were present in affected habitats during subsequent intermittent hypoxia. The vertical distribution of macrobenthos in sediment changed significantly with season, with overall lower abundance at depth in sediment during hypoxia than in normoxia; however, this trend was not always clear or consistent with changes in water-column oxygen concentrations. Alternative factors that may account for such patterns (e.g., recruitment pulses) are discussed. The intensity of hypoxia was correlated with changes in benthic community structure and distribution. Results suggest that the periodicity of hypoxic events may lead to long-term alterations of benthic populations, largely as a reflection of the varying species tolerances and life-histories.

Serum Transferrin Polymorphism in Grey Trout, Cynoscion regalis, from the Lower Rappahannock River

Serum transferrin distribution was studied in grey trout, Cynoscion regalis, obtained from the lower Rappahannock River of Virginia. Three phenotypes were observed, representing two codominant alleles at a single gene locus. The distribution of the phenotypes, designated as Tf A, Tf B, and Tf AB, did not differ significantly from that predicted by Hardy-Weinberg analysis.