Factors in the Decline of Coastal Ecosystems

Abstract

In their review "historical overfishing and the recent collapse of coastal ecosystems," Jeremy B. C. Jackson and colleagues argue for the "primacy" of overfishing in the collapse, in contrast to pollution, species introductions, climate change, diseases, and other human impacts (special issue on Ecology Through Time, 27 Jul., p. 629). They suggest that overfishing had the earliest impacts and was a necessary precondition for the occurrence of other maladies. Although we agree that fishing has contributed to major changes in coastal ecosystems, we believe Jackson and co-authors overstate the case for its primacy. The overfishing and nutrient pollution of coastal seas, for example, have frequently proceeded simultaneously and contributed to degradation synergistically (1).In Chesapeake Bay, as the authors point out, the process of eutrophication began with land clearing in the 18th century, well before the mechanized harvest of oysters in the late 19th century. Although most of the filtration capacity of oyster populations had been reduced by the 1930s, the dramatic intensification of hypoxia and the extensive loss of seagrasses occurred later, during the last half of the 20th century, associated with a more than doubling of the already elevated nitrogen loading (2).Recognizing that rebuilding oyster populations could help to mitigate planktonic overproduction due to nutrient pollution (3), the multistate Chesapeake Bay Program has established the ambitious goal of a 10-fold increase in oyster biomass. But restoration of oysters even to precolonial abundances is unlikely to eliminate algal blooms and hypoxia and recover seagrasses without also significantly reducing nutrient loading. Decreasing bottom-up stimulation and increasing top-down controls will be required.Although the degradation of oyster reefs by overfishing might have made oysters more susceptible to endemic diseases, a particularly virulent pathogen (Haplosporidum nelsoni) was introduced from a nonindigenous oyster host in the 1950s (4). This introduced disease now greatly limits the ability to reestablish oyster populations.Similarly, it is not likely that intact populations of large consumers, such as green turtles and sea cows, would have prevented the deleterious consequences of nutrient pollution, sedimentation, and other human-induced stresses on tropical seagrass ecosystems witnessed in the late 20th century in such regions as Australia (5) and Florida Bay (6). And there were no similar large consumers of temperate seagrasses, which have also undergone decline. Regardless of the historical sequence of human stresses, amelioration of multiple stresses must take a multi-pronged approach to restore coastal ecosystems. ResponseOur review is indeed about the deep historical roots of human degradation of a diverse suite of coastal marine ecosystems, caused by and preconditioned by fishing exploitation and attendant damage to biogenic marine habitats. The novelty of our study lies in its use of multiple associated disciplines, such as paleontology, ...

Temporal and spatial distributions of nutrients under the influence of human activities in Sishili Bay, northern Yellow Sea of China

“…Nutrient limitations vary based on the different biogeochemistry within and between ecosystems and different seasons (Boesch et al, 2001). In our study, 79% of DRSi/DIN ratio values were less than 1.…”

Drained coastal peatlands: A potential nitrogen source to marine ecosystems under prolonged drought and heavy storm events—A microcosm experiment

“…Overloading of nitrogen is a leading cause of impairment of coastal marine ecosystems around the world (Boesch et al, 2001;Compton et al, 2011;Diaz and Rosenberg, 2008;Paerl and Piehler, 2008). Currently, most studies focus on anthropogenic nitrogen sources, like fertilizer applied in farmlands and fossil-fuel derived atmospheric deposition Liu et al, 2013;Paerl, 1997;Paerl, 2009;Robert, 2008).…”

“…Importantly, drought durations are projected to increase in the future (IPCC, 2007), which could substantially increase the available nitrogen pool in peatlands. Therefore, large quantities of nitrogen in peatlands would likely be released to freshwater bodies during heavy storms and subsequently enter coastal estuarine and marine ecosystems with negative consequences (Boesch et al, 2001;Diaz and Rosenberg, 2008;Paerl and Piehler, 2008).…”

Anthropogenic and climatic influences on the eutrophication of large estuarine ecosystems

“…Large increases in pollutant discharge have accompanied the agricultural and urban development of coastal watersheds (Peierls et al 1991;Hopkinson and Vallino 1995;Boesch et al 2001). Deterioration of estuarine ecosystems that process this burgeoning nutrient load is accelerating, yet there is a paucity of information on how primary producer and higher-ranked consumer com-munities are being altered.…”