Title

Data from: Individual, population, and ecosystem effects of hypoxia on a dominant benthic bivalve in Chesapeake Bay

Document Type

Data

DOI

10.5061/dryad.c45f0

Publication Date

1-1-2013

Description

Hypoxia is an environmental stressor that affects abundance, biomass, diversity and ecosystem function of benthic assemblages worldwide, yet its collective impact at individual, population, and ecosystem levels has rarely been investigated. We examined the effects of hypoxia on the biomass-dominant clam, Macoma balthica, in the York and Rappahannock Rivers (Chesapeake Bay, USA). We (i) surveyed the M. balthica populations in both rivers in 2003 and 2004, (ii) determined the effects of low DO on M. balthica fecundity in a laboratory experiment, and (iii) employed a predator-exclusion field experiment to establish the effects of hypoxia and prey density on predation upon M. balthica. The resultant data were used to parameterize a matrix model, which was analyzed to define potential effects of hypoxia at the population level. In both rivers, hypoxia decreased individual clam growth and caused local extinction of populations. Hypoxia reduced egg production of M. balthica by 40% and increased protein investment per egg. In the predator-exclusion field experiment, hypoxia magnified predation rates three-fold and altered the functional response of predators to M. balthica from a stabilizing type III functional response to a destabilizing type II functional response. In a density-independent matrix model, hypoxia resulted in coupled source-sink metapopulation dynamics, with hypoxic areas acting as black-hole sinks. Increases in the spatial and temporal extent of hypoxia caused the populations to decline toward extinction. In a second model that incorporated density-dependence, under mild hypoxic conditions trophic transfer from M. balthica to predators increased, but at increased spatial or temporal extent of hypoxia trophic transfer decreased. The major decline in trophic transfer to predators under severe hypoxia resulted from diversion of M. balthica biomass into the microbial loop. Our model predicted that there are multiple stable states for M. balthica populations (high and very low densities), such that the saddle point (threshold at which the population switches from one state to the other) increased and resilience decreased with the spatial extent of hypoxia. We underscore how effects of a stressor at the individual level can combine to have substantial population and ecosystem-level effects.,Sites and physical measurements 2003GPS coordinates and measurements of dissolved oxygen, temperature, and salinity taken during field surveys in the York and Rappahannock Rivers, VA, in 2003.Sites and physical measurements 2004GPS coordinates and measurements of dissolved oxygen, temperature, and salinity taken during field surveys in the York and Rappahannock Rivers, VA, in 2003.Field predation and non-predatory mortality ratesCalculated predation rates from a caging study on Macoma balthica in the York River in 2006. Rates were calculated based on the number of marked clams recovered after approximately 4 weeks exposure time. Non-predatory mortality rates were based on the recovery of marked dead clams (i.e. undamaged shells). The major predator on M. balthica in this system is the blue crab Callinectes sapidus.Field predation experiment DO DatasondThis file contains the measurements of dissolved oxygen (DO) in mg O2/L recorded by a Hydrolab DS5X with a luminescent DO probe (Hach Environmental, Loveland, CO) at a single deep site during the predation experiment in the York River in 2006. Date/time represents the data and time (EST) of each measurement.Field predation sites and physical measurementsThis file contains the measurements of dissolved oxygen (DO) in mg O2/L at each site during the predation experiment using an YSI 85. Date represents the date of each measurement. Latitude and longitude are in decimal degrees. Temperatures are in degrees Celsius, salinity in practical salinity units (psu) and dissolved oxygen (DO) in mg O2/L.Lab experiment DO and tempThis file contains the measurements of dissolved oxygen (DO) and temperature in tanks during a laboratory experiment examining the effects of low DO on the clam Macoma balthica. Treatment represents the nominal dissolved oxygen (mg O2/L) treatment group. Replicate represents the replicate tank number. DO is in mg O2/L) and temperature is in degrees Celsius. The date is the date of each measurement and time is approximate time in EST.Macoma balthica densitiesThis file contains the average Macoma balthica densities at each site sampled in box cores during the field surveys in 2003-2004. The minimum summer DO represents the minimum dissolved oxygen concentration (mg O2/L) observed at each site during that year. River is represent the river the sample was taken in, Date the day the sample was taken, and Site the nominal site at which the sample was taken. Note that sites changed location between years, (i.e. site M2 in 2003 in the York was at a different location than site M2 in 2004). Site location and raw DO measurements are available in the Sites and physical measurements files.Macoma balthic densities.csvMacoma balthica lengths and massesThis file contains the average Macoma balthica shell lengths in mm and ash free dry masses (AFDM) in mg at each site sampled during the field surveys 2004. River represents the river the sample was taken in, Site represents the site name, Date represents the date the sample was taken. The average summer DO represents the average dissolved oxygen concentration (mg O2/L) observed at each site during that summer. Site locations and raw DO measurements are available in the Sites and physical measurements 2004 file.Macoma balthic lengths and masses.csvMacoma balthica recruitsThis file contains the Macoma balthica recruit (shell length < 3 mm) densities at each site sampled during the field survey in the Rappahannock River in Feb. 2004. River represents the river the sample was taken in; Site represents the site name; Date represents the date the sample was taken. The minimum summer DO represents the minimum dissolved oxygen concentration (mg O2/L) observed at each site during that year. Site location and raw DO measurements are available in the Sites and physical measurements files.Macoma balthic recruits.csvMacoma balthica shell lengthsThis file contains the Macoma balthica shell lengths (in mm) at each site sampled during the field surveys 2004. River represents the river the sample was taken in, Site represents the site name, Date represents the date the sample was taken. The average summer DO represents the average dissolved oxygen concentration (mg O2/L) observed at each site during that summer. Site location and raw DO measurements are available in the Sites and physical measurements files.Macoma balthic shell lengths.csvMacoma balthica survivalThis file contains the average Macoma balthica survival at each site sampled during the field survey in 2004. Survival is calculated as the average density in the fall sampling divided by the average sampling in the spring at each site. River represents the river the sample was taken in, Site represents the site name, Date represents the date the sample was taken. The average DO represents the average dissolved oxygen concentration (mg O2/L) during the summer months observed at each site during that year. Site locations and raw DO measurements are available in the Sites and physical measurements files, and the raw densities are available in the Macoma balthica densities file.mb-HSP70 and fecundityThis file contains the measurements units mb-HSP70/clam and the number of eggs/clam in the laboratory experiment. Examining the effects of dissolved oxygen on Macoma balthica. Mb-HSP70 is a protein expressed in Macoma balthica. Eggs/clam could only be calculated for the > 4.0 mg/L treatment, and the < 2.0 mg/L treatment; blank indicate no data is available. Treatment represents the nominal dissolved oxygen (mg O2/L) treatment group. Replicate represents the replicate tank number within each treatment.mb-HSP70 and protein in eggsThis file contains the measurement of units mb-HSP70/egg and the µg protein/egg in a laboratory experiment on the effects of dissolved oxygen on Macoma balthica. Mb-HSP70 is a protein expressed in Macoma balthica eggs. Treatment represents the nominal dissolved oxygen (mg O2/L) treatment group. Clam represents the replicate clam number.,

Publisher

DRYAD

Source Link

http://datadryad.org/stash/dataset/doi:10.5061/dryad.c45f0

Version

1

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