Oceanic heat waves tend to happen due to abnormal patterns in weather which result in an increased amount of heat being driven into the ocean, instilled within the surface of the ocean, or block heat from exiting the ocean. Marine heatwaves can also be attributed to climate change, with climate change enabling the mere existence of marine heatwaves to be 20 times as likely than without global warming.
Marine heatwaves have various negative impacts on aquatic organisms living in oceanic ecosystems, not limited to but including the following: coral reef bleaching, destruction of kelp and additional aquatic vegetation, and a reductive shift in reproduction/survival of many oceanic creatures.
Specifically within the West Coast, zooplankton was found to be significantly smaller in size according to NOAA (National Oceanic Atmospheric Administration) Research. This negatively affects aquatic animals that consume zooplankton, such as small fish or seabirds, due to the lack of calorie and fat content within the zooplankton.
Additionally, a relationship between the increased presence of marine heatwaves in relation to the increased presence of harmful algal blooms can also be examined. In 2013, a NCCOS (National Centres for Coastal Ocean Science)-sponsored study found that the recurrent marine heatwaves on the West Coast of the US directly resulted in an increase of detrimental algae, spreading every year since 2015. The aftermath consisted of the shutdown of harvesting shellfish and Dungeness crab. In regards to marine life, algal blooms have caused various aquatic mammals to become victims of eating contaminated fish and other poisoned substances. This was seen around summertime in the Puget Sound area according to Nick Bond, a scientist with a NOAA cooperative institution.