Sea-surface temperatures in the Northeast Shelf Large Marine Ecosystem during 2012, which includes the waters off Martha’s Vineyard, were the highest recorded in 150 years, NOAA’s Northeast Fisheries Science Center (NEFSC) reported in an Ecosystem Advisory issued last week.
These high sea-surface temperatures (SSTs) are the latest in a trend of above-average temperatures seen during the spring and summer seasons, and part of a pattern of elevated temperatures occurring in the Northwest Atlantic, but not seen elsewhere in the ocean basin over the past century, NOAA said.
Sea surface temperature for the Northeast Shelf Ecosystem reached a record high of 57.2°F in 2012, exceeding the previous record high in 1951. Average sea surface temperature has typically been lower than 54.3 F over the past three decades.
NOAA has been measuring water temperatures since 1854. The temperature increase in 2012 was the highest jump in temperature seen in the time series and one of only five times temperature has changed by more than 1.8 F, NOAA said.
The Northeast Shelf’s warm-water thermal habitat was also at a record high during 2012, while cold water habitat was at a record low level. Early winter mixing of the water column went to extreme depths, which will affect the spring 2013 plankton bloom. Mixing redistributes nutrients and affects stratification of the water column as the bloom develops.
Temperature is also affecting distributions of fish and shellfish on the Northeast Shelf. The NOAA advisory provides data on changes in distribution, or shifts in the center of the population, of seven key fishery species over time. The four southern species — black sea bass, summer flounder, longfin squid, and butterfish — all showed a northeastward or upshelf shift. American lobster has shifted upshelf over time but at a slower rate than the southern 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,” Jon Hare, a scientist in the NEFSC’s Oceanography Branch said.
In 2009, a NOAA study found that about half of the 36 fish stocks studied in the Northwest Atlantic Ocean, many of them commercially valuable species, have been shifting northward over the past four decades.
Warming conditions on the Northeast Shelf in the spring of 2012 continued into September, with the most consistent warming conditions seen in the Gulf of Maine (GOM) and on Georges Bank (GB). Temperatures cooled by October and were below average in the Middle Atlantic Bight (MAB) in November, perhaps due to Superstorm Sandy, but had returned to above average conditions by December.
“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. He noted that the contrast between years with, and without, a fall bloom is emerging as an important driver of the shelf’s ecology. “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. ”
Mike Fogarty, who heads the Ecosystem Assessment Program, says the abundance of fish and shellfish is controlled by a complex set of factors, and that increasing temperatures in the ecosystem make it essential to monitor the distribution of many species, some of them migratory and others not.
“What these latest findings mean for the Northeast Shelf ecosystem and its marine life is unknown,” Mr. Fogarty said. “What is known is that the ecosystem is changing, and we need to continue monitoring and adapting to these changes.”
Ecosystem advisories have been issued twice a year by the NEFSC’s Ecosystem Assessment Program since 2006 as a way to routinely summarize overall conditions in the region. The reports show the effects of changing coastal and ocean temperatures on fisheries from Cape Hatteras to the Canadian border. The advisories provide a snapshot of the ecosystem for the fishery management councils and also a broad range of stakeholders from fishermen to researchers.