SEA-News: The Demise of Phytoplankton; Earths ultimate Producer

December 31, 2010

by Jake Sultan
SEAlliance Contributor

Plankton Rich Water, Purple Striped Jelly (c) Kip Evans

Phytoplankton are the oceans major consumer of carbon dioxide, a primary producer of atmospheric oxygen, and the base to any marine food web. In general, these tiny organisms that are often only visible through a microscope, make up the majority of plant-like material in the ocean. Tiny as they may be, these organisms are one of the most important living things on Earth, as they account for over half of the global primary production (the organic compounds that are built up by photosynthesis over time). Unfortunately phytoplankton abundance and diversity is reducing at a significant rate. Studies conducted by Canadian scientists revealed that over the past century there has been a consistent decrease in the number and diversity of marine phytoplankton, while the greatest loss continues to occur in the open ocean where phytoplankton primary production is highest. Although far removed from the mainland, and unknown to most people, the loss of these vital organisms can jeopardize the health of the planet.

A decline in phytoplankton production not only affects the marine ecosystem but also influences the terrestrial planet. A significant portion of the earths atmospheric oxygen (anywhere from 20-50%) is produced by these microscopic organisms, so without them life on earth would certainly be threatened. Recent research has shown that phytoplankton in the Northern Hemisphere has declined nearly 40% since 1950 and is currently declining at an overall average of 1% per year. While it is unclear why this decline is occurring, it is almost certain that humans are playing a part in its reduction and therefore must develop solutions to avoid further destruction.

Jack Mackerel Feeding (c) Kip Evans

One solution to reducing the loss of phytoplankton is to maintain its diversity in order to ensure that various species are as efficient as possible in their production. Species diversity increases the natural sustainability, survival rate, and recovery of phytoplankton populations from a variety of disturbances and disasters. Without this diversity, entire populations could be wiped out through a single environmental event, thus destroying an entire ecosystem. Currently, the greatest diversity of phytoplankton exists in tropic and sub-tropic areas. These populations are declining due to rising sea surface temperatures (SST) and temperature stratification, which may be a result of climate change and an increased exposure to UV radiation. This increased SST leads to shallower mixed layers that limit vertical mixing and the movement of nutrients throughout the ocean, which in turn threatens the health of phytoplankton. As a result the nutrient rich cold water is kept from reaching phytoplankton at the surface thus depriving it of vital nutrients needed for growth. Generally, the more stratified or layered water is by temperature the more difficult it is for nutrients to mix, therefore making it difficult for phytoplankton to access needed nutrients.

In addition to the loss of diversity in the phytoplankton abundant tropical zones, phytoplankton diversity tends to decrease with increasing latitudes. This occurs because the seasonal variability of water in the higher latitudes is often dominated by opportunistic phytoplankton that can quickly grow and effectively utilize available resources. Through competitive exclusion, the faster-growing organisms can control more resources and prevent less adapted species from growing, which ultimately leads to less diversity of phytoplankton. These higher latitude locations are particularly important areas to study and protect because they are increasingly at risk to climate shifts or unfamiliar disturbances due to their lack of diversity.

Because phytoplankton plays such a vital role in the health of the Earth’s ecosystem, it is critical that a better understanding of these tiny organisms is established. As the planet conforms to the anthropogenic induced changes that are occurring, it is important to take into account the impacts humans have on the marine ecosystem. By being aware that phytoplankton are not only important to the marine ecosystem but also the terrestrial planet, it is possible to raise awareness and a need for its protection. While most Marine Protected Areas (MPAs) have been established in coastal areas, it is important that they are also created in phytoplankton hot spots as well. These areas can allow for natural trophic systems to form and function, thus maintaining diversity and the overall health of the marine ecosystem, which in turn can improve the health of the Earth as a whole.