The key to reducing the size and number of low-oxygen dead zones in coastal waters is to reduce the input of nutrients into estuaries and the coastal ocean. Nutrient-reduction strategies are a key part of efforts to restore the health of Chesapeake Bay.
Researchers at the Virginia Institute of Marine Science (VIMS) collaborate with colleagues around the world to address the problem of marine dead zones, including efforts to
- understand how dead zones form,
- decipher how dead zones affect marine organisms and communities,
- monitor and model dead-zone prevalence and duration,
- develop criteria to gauge the severity of dead zones, and
- provide guidance to policymakers and resource managers concerning the land-use and water-quality strategies needed to reduce dead-zone formation.
An important strategy in reducing the size and duration of dead zones is establishment of a total daily maximum load (TMDL) for the nutrients (nitrogen and phosphorus) that encourage dead-zone formation. TMDLs are similar to the "recommended daily allowances" found on food labels, and indicate the maximum amount of a pollutant that can enter a water body without causing a water-quality indicator such as dissolved-oxygen levels to cross a defined threshold.
Water-quality thresholds can vary depending on a water body's "designated use." These include use by native marine life, commercial harvesting of fish and shellfish, and recreational uses such as swimming and boating. The thresholds also recognize seasonal variations in nutrient inputs and dissolved-oxygen levels, as well as difference in dissolved-oxygen levels in different Bay habitats.
VIMS researchers work with colleagues in state and federal agencies on all 3 steps of the TMDL plan for nutrient pollution that was set forth in the Chesapeake 2000 Agreement:
- Develop the TMDLs needed to meet water-quality standards.
- Develop a TMDL implementation plan.
- Implement the TMDL plan, and monitor water quality to determine if water-quality standards are being attained.
Read more about VIMS' role in the TMDL program for nutrient pollution in Chesapeake Bay:
Selected Journal Articles
- Batiuk, R.A., Breitburg, D.L., Diaz, R.J., Cronin, T.M., Secor, D.H., Thursby, G., 2009. Derivation of habitat-specific dissolved oxygen criteria for Chesapeake Bay and its tidal tributaries. Journal of Experimental Marine Biology and Ecology 381, S204-S215.
- R.J. Diaz and R. Rosenberg, 2008. Spreading dead zones and consequences for marine ecosystems, Science 321: 926–929.
- Alessandra Sagasti, L.C. Schaffner, J. Emmett Duffy, 2001. Effects of periodic hypoxia on mortality, feeding and predation in an estuarine epifaunal community. Journal of Experimental Marine Biology and Ecology 258 (2): 257-283.
- Diaz and Rosenberg, 1995 Marine benthic hypoxia: a review of its ecological effects and the behavioral responses of benthic macrofauna, Oceanogr. Mar. Biol., Annu. Rev. 33: 245–303.
- Diaz et al., 1992 R.J. Diaz, R.J. Neubauer, L.C. Schaffner, L. Pihl and S.P. Baden, Continuous monitoring of dissolved oxygen in an estuary experiencing periodic hypoxia and the effect of hypoxia on macrobenthos and fish, Sci. Total Environ. (1992): 1055–1068 Suppl. 1992.
- Pihl, L., S.P. Baden, R.J. Diaz and L.C. Schaffner. 1992. Hypoxia-induced structural changes in the diet of bottom-feeding fish and crustacea. Mar. Biol. 112:349-361.
- Pihl, L., S.P. Baden and R.J. Diaz. 1991. Effects of periodic hypoxia on distribution of demersal fish and crustaceans. Mar. Biol. 108:349-360.