Welcome to ClimateGenn and I am Nick Breeze. The following is an update from a post a year ago looking at the impacts on marine ecosystems with the 2024 data on dolphins that came in for the Galician coast in NW Spain.
Doniños beach is a 2km (1.18mile) stretch of sweeping sandy shoreline, exposed to the wild roar of Galicia’s Atlantic waves. At this time of year it is shrouded in a fine sea mist. About midway along the beach a colony of shearwaters takes flight as they eye our arrival.
It is only when we are closer to where they were gathered that we see a large common dolphin lying dead, mouth agape in a jovial toothy smile. Later, further along the beach, we spotted another dolphin lying with the familiar grimace, covered in flies, rotting on the shore. This one, smaller in size, had been dead longer.
“There are days with one dead dolphin, other days with nine.”
Mónica González – Galician Stranding Network (CEMMA)
Last year I met with the Galician Stranding Network team who were giving a lecture at the University of Coruna. This tight squad of three operatives spend an exhaustive amount of time responding to cetacean stranding’s, performing autopsies to determine causes of death and evaluate the general health of marine wildlife along the coast. Cetaceans include a number of species of dolphins, but the most frequent that are found stranded along the shore are (in decreasing order) the common, bottlenose and striped dolphins, as well as the harbour porpoise.
During my meeting we discussed what was causing the incidences of dolphin deaths to surge by over 2.7 times. Between the years 2000-2022 the mean average of stranded dolphins found along the coast was 227. In 2023 and 2024 the numbers spiked to 618 and 614 respectively. The figure for dolphins as victims of bycatch is stable at around 50%. Bycatch refers to the unintentional capture and subsequent death of a species in fishing nets or gear intended for other marine species. The marine scientists at CEMMA and University of Santiago suspect the other 50% of deaths are related to a lack of food further out to sea.
Food shortage in deeper waters
The strong Atlantic currents that circulate heat from the tropics to the north Atlantic, flow past the Galician coast and have been weakening due to the increase in atmospheric carbon dioxide. The Galician Stranding Network chief, Alfredo López, describes these currents as a “super highway”. Normally dolphins and whales are on the super highway and don’t come into shore here.
These hotter Atlantic Ocean temperature anomalies hit record highs in 2023 and persisted higher into 2024. The temperature rises of the ocean waters have been so dramatic that many experts fear the super highway is not just slowing down but could eventually stop altogether.
Marine ecosystems under pressure
With a hotter and more acidic ocean, the tiny phytoplankton that thrive in the top layer of the sea-surface start to die off. This in turn impacts the zooplankton, like krill and tiny jellyfish, that are food for small fish like herring or anchovy, that in turn are food for medium sized fish and birds. A break in this chain ricochet’s up to the larger predators such as marine mammals who find the fish they rely on for food are gone.
Coming in to feed
As the ecosystems in the deeper waters of the Atlantic decrease, more dolphins, whales, turtles and sharks are coming into the coastal areas in search of food. Galician coastal waters are also home to one of the most famous fishing regions in the world. Seafood in this quiet north west corner of Spain is tightly woven into the fabric of the culture.
Dolphins who have lived in close to shore for many years are more likely to survive due to being familiar with fishing practices and areas where tides can drain away fast. New comers to the coast are at a much higher risk of stranding or getting caught up in fishing gear. Alfredo suggests that it is a combination of these factors that are driving up the number of dead dolphins along the Galician coast.
Wider impact
Seafood dominates the menu of every bar and restaurant along the Galician coast. The prices are rising steeply as scarcity increases. Baby clams are being brought in from tropical latitudes and are buried in the saltwater river valleys to mature for harvesting. It is their suitability to rising water temperatures that is driving this practice, displacing struggling indigenous varieties.
With the overall all die-off of shell fish such as mussels, clams, cockles and oysters, occurring in the region, the future health of Atlantic ecosystems in Galicia looks bleak. The ocean warming and acidification is causing a cascade of secondary impacts that are decimating the oceans and risk wiping out vast populations of dolphins and a large portion of the fishing industries in Galicia. The underlying key driver is the extra heat in the Earth system from continued use of coal, oil and gas.
The increasing corpses of dead dolphins strewn about the beach is a more overt signal that all is not well on planet Earth.
