Lowell Instruments LLC partnered with the Lobster Foundation of Massachusetts, Massachusetts Lobsterman’s Association, and the Massachusetts Division of Marine Fisheries (MA DMF) to launch a study with a fleet of lobster boats, to monitor dissolved oxygen (DO) levels in Cape Cod Bay. This study was in response to hypoxic conditions (lack of oxygen) that occurred in Cape Cod Bay in October of 2019, when fishermen were pulling up their lobster traps and found a large number of dead lobsters.
When the MA DMF studied the dead lobsters, they discovered that they had died from a lack of oxygen. Low oxygen levels are not entirely unexpected in the fall, according to researchers, however the severely hypoxic conditions in 2019 had never been reported before in Cape Cod Bay. Warm summers can create layers in the water column, with the warmest water exposed to the air at the surface, and cooler waters trapped near the bottom unable to mix with the oxygen-rich surface waters. The fall often arrives with strong winds and waves that cool the surface waters and mix the water column, ensuring that oxygenated water near the surface mixes with the denser, cooler water below. Without storms to stir things up, bottom waters aren’t mixed with surface waters, and oxygen near the bottom is slowly depleted creating a condition known as hypoxia. Some creatures can sense these diminishing oxygen levels and seek out more oxygenated waters, but others that cannot move quickly enough eventually suffocate in the very water that should sustain them. These hypoxic conditions cause stress and/or death in bottom-living organisms, such as lobsters, and are known as a ‘dead zone.’
We created a new wireless data logger that mounts inside the lobster traps, and records DO levels and temperature while the trap is underwater. When the lobstermen pull up the traps in their normal day-to-day fishing, the sensors automatically upload the information to our On-Deck Data Hubs on the boats. The data are then sent to the cloud via cellular modem so that MA DMF can monitor fluctuating DO levels, and can notify the fishing fleet to move their traps out of the dead zone. This pilot study currently has twenty-five DO sensors in lobster traps throughout Cape Cod Bay, partnering with five different lobstermen. The new technology is helping fishermen and scientists understand what is going on in the ocean.
In the last week of August 2020, the southern portion of Cape Cod Bay, experienced very low DO (hypoxia), less than 2 mg/L In several locations sampled. Prolonged exposure to these levels can be deadly to benthic organisms that are not able to move and avoid the area. Lobstermen were notified of these low DO areas and were able to move their traps to areas with normal DO values, where it is safe for lobsters.
Researchers from the Center for Coastal Studies collected additional data to help pinpoint more detailed DO readings throughout the water column. This is the same area that experienced the low DO event and lobster mortalities in the fall of 2019. It is unclear how long these conditions last, but DMF and the Center for Coastal Studies will continue to monitor the region, in collaboration with oceanographers from Woods Hole Oceanographic Institution. This study will continue for the summer and fall of the next two years. Funding for the Lobster Foundation of MA study fleet and Lowell Instruments was provided by the Massachusetts Climate Change Resilience in Fisheries and Aquaculture Grant Program. Funding for additional sampling and oceanographic analyses is being provided by the National Sea Grant Lobster Initiative to MA DMF, Center for Coastal Studies, and Woods Hole Oceanographic Institution.
In The News:
Cape Cod Times: Low oxygen areas show up, again, in Cape Cod Bay worrying lobstermen, scientists
Map of Near Real-Time Dissolved Oxygen Readings from Cape Cod Bay Study Fleet
The Provincetown Independent: Lobstermen Face Hypoxia in Outer Cape Waters - Low oxygen levels linked to warmer water spell trouble for local lobsters
Read our application story about the Dissolved Oxygen Study with Lobster Fleet in Cape Cod Bay HERE
CBS News Eye on Earth - Reported by Jacob Wycoff
Cape Cod Times: The Blob -Low Oxygen Water Killing Lobsters and Fish in Cape Cod Bay
WBUR: Researchers say 'The Blob' on Cape Cod Could Cause Major Environmental Problems
Mass.Gov: Monitoring the Formation and Movements of Hypoxic Water Mass in Cape Cod Bay
Massachusetts Division of Marine Fisheries 2020 DO Monitoring Study: 2020 MA DMF DO event report FINAL