referring to the modern day, human-induced increase in global surface temperatures. This comes with a range of associated problems, and is extremely harmful to flora and fauna throughout the world. Although the effects of global warming on the ocean aren’t often publicized, many marine species are threatened by the earth’s changing climates. Just some of the changes to the ocean are a decrease in pH, an increase in sea surface temperature, and rising sea levels¹. Some of the species affected by global warming will be touched on here due to space constraints, but it is fair to say that every organism on the planet is affected in some way by climate change.
The effects on marine mammals
Since marine mammals are some of the largest species in the ocean, they rely heavily on predator-prey interactions at lower trophic levels. If these interactions are disrupted, then marine mammals may find themselves without a food source, and therefore will suffer².
Of particular concern is the effects of climate change on mammals close to the poles – especially in the Arctic. Animals like polar bears and leopard seals are rapidly losing habitat as sea ice melts and ice sheets break up, which is putting huge pressure on the continued existence of these species¹.
Over the past few decades, melting sea ice in the Antarctic has been identified as a major threat to migratory blue whales. The blue whale’s main food source is krill, which in turn eat microscopic green algae. These algae live in and on sea ice, and the reduction of sea ice means that the food source of the krill is being destroyed. This means less food for blue whales – especially when combined with the fact that humans also catch krill for food source and other things³.
The effect on corals and shellfish
Both corals and shellfish rely on the carbonate ion (CO3-) as a major building block of their skeletons and shells respectively. As atmospheric carbon dioxide (CO2) levels increase, a lot of this CO2 dissolves in the ocean. Here it reacts with water to form the bicarbonate ion, and increases the acidity of the ocean. This in turn reduces the concentration of CO3- in sea water. It also increases the solubility of calcium carbonate, which is the main component of shells and corals⁴.
Both of these things make it more difficult for species to fix calcium carbonate and build their skeletons, which in turn harms the individual organisms. For example, many coral reefs throughout the world are experiencing bleaching due to increased environmental stress caused by warmer water and an increase in ocean acidification. Many of these reefs have been destroyed beyond recovery, and others are on the edge of destruction⁴.
There are many other less obvious impacts on marine species throughout the world. These include:
- Forced migrations
- Rising sea levels
- Increased occurrence of severe weather events