Sea temperature is posing a new threat to the delicate balance of the ocean, affecting even the ocean’s smallest but most important inhabitants: phytoplankton. These microscopic algae provide nutrients to countless marine species and play a critical role in regulating our planet’s climate.
Phytoplankton: heroes of the ocean
phytoplankton — the unsung heroes of our oceans who work behind the scenes to keep marine ecosystems thriving. Although invisible to the naked eye, these microscopic algae constantly produce organic carbon through photosynthesis and support nearly every level of the marine food web.
They also play an important role in the ocean carbon cycle, making a significant contribution to regulating the Earth’s climate. Spring was traditionally their peak. As winter ends, nutrient-rich water from the depths of the ocean rises to the surface, causing a burst of growth known as a phytoplankton bloom.
But recent research shows that this important phytoplankton bloom faces a serious and potentially long-term threat.
The warmth of the sea spoils the spring flowers
The research was carried out by experts from the Italian National Research Council (CNR-ISMAR) Institute of Marine Sciences within the framework of the ESA CAREHeat project. Researchers examined phytoplankton blooms in the northwestern part of the Mediterranean Sea. They found that marine heat waves, that is, prolonged periods of unusually warm seawater, disrupted the timing and intensity of this important spring phytoplankton bloom.
Marine heat waves in winter are particularly threatening because they increase the stratification of ocean water. In other words, they prevent nutrients from deep sea layers from mixing with surface waters.
Warmer water can lead to a significant reduction in the carbon biomass of phytoplankton by up to 70% during the spring bloom. This drastic reduction means fewer nutrients are available, leading to a change in the balance of the marine food web.
Ripple effects in the food chain
“We noticed that intense sea heat in winter delays the bloom time of phytoplankton. This shift causes a mismatch in the availability of zooplankton that depend on these blooms for food, potentially affecting fish and other marine species that depend on zooplankton,” explained study co-author Emanuele Organelli.
Additionally, intense sea heat can affect the ecosystem’s ability to absorb carbon, which is critical to global climate regulation. If these disturbances continue, the balance of marine biodiversity may be disrupted and both local habitats and global processes may be affected.
Tracking sea temperature and ocean conditions
To better understand and solve this growing problem, researchers have turned to technology. They used sea surface temperature data from ESA’s Climate Change Initiative (ESA CCI) and various satellite platforms such as the Copernicus Sentinel-3 Sea Surface and Land Temperature Radiometer.
This allowed experts to track and classify temperature events in the Mediterranean from 2012 to 2022.
“ESA’s continuous satellite monitoring is critical to track and address these increasing threats to marine biodiversity,” said ESA scientist Marie-Hélène Riot. “The increasing frequency of marine heatwaves could further threaten vital ocean services such as fisheries and the oceans’ ability to absorb carbon, which are key to both marine ecosystems and global climate stability.”
These tiny marine allies need our help, and monitoring marine heatwaves could be our first step towards preventing a potentially devastating ripple effect on marine ecosystems.
Implications for marine ecosystems
Marine heat waves not only affect phytoplankton, but also destroy entire ocean ecosystems. As these tiny algae struggle to bloom, animals higher up the food chain like fish, seabirds, and even marine mammals may find less food to eat. Food shortages can lead to changes in where species live and how they interact.
For coastal communities, these disruptions also affect those close to home. Many rely on fishing to feed their families, and fewer fish can mean a harder life for these communities. There is also a risk that climate change will accelerate further, as phytoplankton absorbs less carbon due to heat waves.
Scientists hope to protect our oceans by closely monitoring marine heat waves. Their work will guide efforts to protect sensitive areas and develop new strategies to combat climate change.
Source: Port Altele
