April 27, 2013
Record High Temps Recorded In The Northeast Shelf Large Marine Ecosystem
April Flowers for redOrbit.com - Your Universe Online
According to the most recent Ecosystem Advisory issued by NOAA's Northeast Fisheries Science Center (NEFSC), sea surface temperatures (SSTs) for 2012 in the Northeast Shelf Large Marine Ecosystem were the highest recorded in 150 years. These record SSTs are the latest in a trend of above average temperatures observed during the spring and summer seasons and part of a pattern of elevated temperatures in the Northwest Atlantic. This trend has not been observed elsewhere in the ocean basin over the past one hundred years.
Both contemporary satellite remote-sensing data and long-term shipboard measurements are used to set SST in the region, with historical SST conditions based on shipboard measurement that date back to 1854. The 2012 increase is the highest jump in temperatures in the time series, and one of only five times the temperature has changed by more than 1.8 degrees Fahrenheit.
Other records were set in the region, as well. The Northeast Shelf's warm water thermal habitat was at a record high, while the cold-water habitat was at a record low level. The 2013 plankton bloom will be affected by the early winter mixing of the water column, which went to extreme depths in 2012. Nutrients are redistributed due to mixing, which affects stratification of the water column as the bloom develops.
Distributions of fish and shellfish on the Northeast Shelf are also affected by temperature changes. The advisory includes data on shifts in the center of the population of seven key fishery species over time. All four of the southern species - black sea bass, summer flounder, longfin squid and butterfish - showed an upshelf, or northeastern, shift. The American lobster has also shifted upshelf, but at a much slower rate than the southern four. Two species — Atlantic cod and haddock — have shifted downshelf.
“Many factors are involved in these shifts, including temperature, population size, and the distributions of both prey and predators,” said Jon Hare, a scientist in the NEFSC´s Oceanography Branch. The changing distributions of fish and shellfish have been documented in a number of recent studies. This supports a 2009 report by NEFSC that about half of the 36 fish stocks studied in the Northwest Atlantic Ocean — many commercially valuable species — have been shifting northward for the last forty years.
Stretching from the Gulf of Maine to Cape Hatteras, North Carolina, the Northeast US Continental Shelf Large Marine Ecosystem (LME) has been monitored by the NEFSC with comprehensive sampling programs since 1977. Separate, coordinated programs, dating back decades, were used to monitor this ecosystem by NEFSC prior to 1977.
The warming conditions of spring 2012 continued into September, with the most consistent warming conditions seen in the Gulf of Maine and on Georges Bank. By October, the temperatures cooled and were below average in the Middle Atlantic Bight in November. November's below average temperatures might be due to Superstorm Sandy, however, by December they had returned to average conditions.
“Changes in ocean temperatures and the timing and strength of spring and fall plankton blooms could affect the biological clocks of many marine species, which spawn at specific times of the year based on environmental cues like water temperature,” Kevin Friedland, a scientist in the NEFSC Ecosystem Assessment Program, said. Friedland noted an important driving factor in the shelf's ecology is the contrast between years with, and without, a fall bloom. “The size of the spring plankton bloom was so large that the annual chlorophyll concentration remained high in 2012 despite low fall activity. These changes will have a profound impact throughout the ecosystem.”
According to Michael Fogarty, head of the Ecosystem Assessment Program, a complex set of factors controls the abundance of fish and shellfish. Increasing temperatures in the region make it vital to monitor the species distribution, as some of them are migratory and some are not.
"It isn´t always easy to understand the big picture when you are looking at one specific part of it at one specific point in time,“ Fogarty said. “We now have information on the ecosystem from a variety of sources collected over a long period of time, and are adding more data to clarify specific details. The data clearly show a relationship between all of these factors.
“What these latest findings mean for the Northeast Shelf ecosystem and its marine life is unknown,” Fogarty said. “What is known is that the ecosystem is changing, and we need to continue monitoring and adapting to these changes.”
Since 2006, NEFSC's Ecosystem Assessment Program has issued Ecosystem Advisories twice a year as a way to summarize overall conditions in the region. From Cape Hatteras to the Canadian border, the advisory shows the effects of changing coastal and ocean temperatures on fisheries and provides a snapshot of the ecosystem for the fishery management councils and other stakeholders.