Low-oxygen 'dead zone' aka The Blob, reappears for third year in Cape Cod Bay
The Blob is back.
Preliminary data from water sampling done by lobstermen and the Center for Coastal Studies in Provincetown indicates that the southern portion of Cape Cod Bay is experiencing decreasing levels of dissolved oxygen along the ocean bottom.
That could kill lobsters and fish caught in traps, and the state Division of Marine Fisheries Wednesday issued a press release asking fishermen to look for and report lethargic or dead lobsters and fish in their traps to scientist Tracy Pugh at tracy.pugh@umass.gov.
While lobsters and fish can move out of an area with low oxygen, shellfish and animals caught in traps cannot.
This is the third year that a so-called Dead Zone, aka The Blob, with low levels of oxygen, has made an appearance in Cape Cod Bay. Lobstermen first reported finding dead or listless animals in their lobster traps in 2019.
The Blob has typically occurred in August and can continue into October in an area that, in both 2019 and 2020, spanned from the entrance to Barnstable Harbor up to Plymouth.
Low oxygen levels have been detected in offshore water from the Barnstable Harbor entrance to East Sandwich so far this year.
Previous coverage: 'The Blob': Low-oxygen water killing lobsters, fish in Cape Cod Bay
Last year, Sea Grant Woods Hole awarded $331,726 in NOAA funding to equip five lobster vessels with 25 sensors to measure dissolved oxygen and other environmental data in the hope of developing a predictive model for when the conditions are right for low oxygen levels. This is the final year of the two-year grant.
One theory being investigated is that currents flowing into Cape Cod Bay from the north get cut off by a change in ocean circulation in the late summer and early fall. That change in ocean circulation, and a lack of storm activity, encourages the water to set up in layers according to temperature and density, known as thermoclines.
Cut off from the oxygen supplied by wave action, oxygen in the bottom layer then gets consumed by the decomposition of organic matter deposited by that northern current.
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