Friday, June 4, 2010
Marine ecology affected by the local weather
As marine scientists, sometimes we forget or don't even realize how much local baymen and fishermen actually know. Or maybe we don't trust them because they are "lay" persons. But they work the bay, they try to catch many of the species we study (as money is a big driver of research), and they know things. Local baymen who have worked the bay for years suggest that bay scallop recruitment is higher in years after cold/wet winters. Sometimes, we take what they say with a grain of salt. However, they know. They have often been working with these species for as long or longer than we have, and it is often also a generation thing. Generations of baymen can't be wrong in their assessment, can they?
A 2001 study in the Dutch Wadden Sea supports these claims, however, their conclusions are not what you think. Matthius Strasser and Carmen-Pia Gunther observed patterns in larval supply of predators and prey after a series of consecutive winters in which temperatures were severe, moderate or mild. Originally, the prevailing thought was that egg production increased after severe winters of many benthos, and this is why recruitment was higher in the following spring. However, their research indicates that the numbers and peaks in recruitment were actually highest in the mild winter. So why isn't recruitment highest during these years? Their theory, a mismatch in the predator and prey larval supply. After severe winters there is a delay in the peak larval supply of the major predators, green crabs, of almost 6-8 weeks. This delay is not as apparent as their bivalve prey, and with the average larval time of the bivalves also being shorter, they settle much earlier than the green crabs and have a potential head start in growth. According to the researchers, this mismatch is what fuels observations of higher recruitment after severe winters.
An alternative scenario is one which was observed in Chesapeake Bay. Using local climate response variables Kimmel et al were able to demonstrate noticeable and significant differences in phytoplankton, copepod, gelatinous zooplankton and finfish abundances and composition between years with "wet" winters and years with "dry" winters. Essentially, wet winters led to an increase of freshwater flow and nutrients into the system, which resulted in higher phytoplankton, more copepods, more ctenophores and higher numbers of striped bass. In years of dry winters, there was less phytoplankton, more scyphomedusae and more menhaden. The basic premise is that the local climate had a significant impact on the community composition of Chesapeake Bay by controlling the amount of fresh water flux into the system.
Both are interesting reads, and the idea of the interplay between climate and marine ecology is one that is becoming even more important to understand with the current climate change scenarios. It is quite clear that atmospheric conditions and local climate can have a fairly significant impact on subsequent year classes - something baymen have been familiar with for decades, if not centuries, but something marine scientists have only been exploring for the past decade, give or take.
Strasser, M. (2001). Larval supply of predator and prey: temporal mismatch between crabs and bivalves after a severe winter in the Wadden Sea Journal of Sea Research, 46 (1), 57-67 DOI: 10.1016/S1385-1101(01)00063-6
Kimmel, D., Miller, W., Harding, L., Houde, E., & Roman, M. (2009). Estuarine Ecosystem Response Captured Using a Synoptic Climatology Estuaries and Coasts, 32 (3), 403-409 DOI: 10.1007/s12237-009-9147-y