Effects of hypoxia and organic enrichment on the coastal marine environment

Abstract

Eutrophication is one of the most severe and widespread forms of disturbance affecting coastal marine systems. Whilst there are general models of effects on benthos, such as the PearsonRosenberg (P-R) model, the models are descriptive rather than predictive. Here we first review the process of increased organic matter production and the ensuing sedimentation to the seafloor. It is shown that there is no simple relationship between nutrient inputs and the vertical flux of particulate organic matter (POM). In particular, episodic hydrographic events are thought to be the key factor leading to high rates of sedimentation and accompanying hypoxia. We extend an earlier review of effects of hypoxia to include organisms living in the water column. In general, fishes are more sensitive to hypoxia than crustaceans and echinoderms, which in turn are more sensitive than annelids, whilst molluscs are the least sensitive. Growth is affected at oxygen concentrations between 6.0 and 4.5 mg O 2 l -1

The hypoxia that developed in a microtidal estuary following an extreme storm produced dramatic changes in the benthos

“…These trends parallel those described for 423 hypoxia and other detrimental effects in other estuaries and coastal waters (e.g. Gray et al 2002) and 424 are consistent with other evidence that crustaceans are far more susceptible than annelids to 425 made an important contribution to the reduction in taxonomic distinctness during this period and 428 which is typical of stressful environmental conditions (Reise 1982 Rosenberg 1994). Nevertheless, the trends in the shade plot (Fig.…”

Sea anemones and brittle stars: unexpected predatory interactions during induced in situ oxygen crises

“…With ongoing oxygen stress, however, the ophiuroids became less active and most ultimately left their perches. Most echinoderms are intolerant of low oxygen concentrations (Gray et al 2002;Levin 2003), and our results conWrm that O. quinquemaculata is a hypoxia-sensitive species in the Northern Adriatic Sea. All died long before the end of the deployments.…”

Subtidal littering: Indirect effects on soft substratum macrofauna?

“…It is noteworthy that comparable LOI% values were recorded in the sediments adjacent to artificial reefs that trapped macroalgal phytodetritus at their periphery (WILDING, 2006). The accumulation of phytodetrital material for longer periods is expected to cause effects similar to that of localized organic enrichment (GRAY et al, 2002). As the phytodetrital mats significantly reduce water movement over the sediment, the bottom water in the mats is often stagnant, resulting in a permanently anoxic sediment surface.…”