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Scientific Records to Illuminate Food Chain

May 25, 2013 | News

Two of the South Carolina coast’s finest scientific records could illuminate complex relationships among tiny but ecologically important creatures—oyster and goby larvae—in estuaries as global climate changes.

Goby larvae inhabit the water column of tidal creeks and eat oyster larvae, selecting them from other plankton. In turn, recreationally important species such as red drum and flounder consume gobies and other small fishes.

Now Sea Grant scientists are studying two data sets taken over more than 30 years from the North Inlet estuary in Georgetown County. The researchers are investigating how increasing water temperature has affected the reproduction, survival, and interactions among oysters and gobies and what impacts these changes might have on the estuary’s food chain.

“We’re interested in how or if the dynamics among oysters and gobies have changed, whether for good or for bad,” says Juliana Harding, a marine biologist at Coastal Carolina University.

Worldwide, many natural communities are being altered as the climate changes. For instance, some prey species are becoming available at different times from their historical predators.

Harding is collaborating with Dennis Allen, director of USC’s Baruch Marine Field Laboratory (BMFL). In North Inlet, Allen and his colleagues have measured winter water temperatures, which indicate an increase of 1.7°C (3.1°F) from 1979-2012, a very rapid warming over such a brief period.

Since 1981, BMFL scientists have also collected zooplankton from the water column. Every two weeks, they have taken samples at the same location, the same stage of the tide, and the same time of day. Larval gobies are one of the more plentiful animals in those collections from May through September each year.

Now, with these two important data sets—winter water temperature and zooplankton abundance—scientists are studying whether the relative timing of goby and oyster larvae in the water column has changed and, if so, what that might mean for both populations. If winter water temperatures increase, will there be a mismatch between predators and the availability of their prey?

One interesting observation from the long-term record at North Inlet is that gobies are hatching later in the spring than expected, when water temperature is warmer. Potential long-term changes in the seasonal availability of oyster larvae are being evaluated using the archived collections.

Ongoing feeding experiments in the laboratory are examining goby larvae consumption of oyster larvae versus other possible planktonic prey. These experiments will provide new insights into the patterns, rates, and mechanisms of changes for these populations and habitats as water temperature continues to warm.

Changes between these two ecologically important species could have ripple effects on other ecosystem relationships, and thus have an impact on estuarine food webs in South Carolina’s tidal creeks, salt marshes, and bays.