The important role phytoplankton plays in our waters: North Fork Outdoors

A microscopic image of phytoplankton.

As the snow and ice begin to melt, our local waters will awaken from their long winter sleep.  An increase in the amount of daylight and an influx of nutrients from winter upwelling and snow/ice melt runoff are catalysts for phytoplankton blooms. 

Microscopic photosynthetic organisms, phytoplankton are responsible for making our bays appear to be dark and murky. For most people, this “dirty” water is unappealing and, in a heartbeat, they would trade it for the crystal-clear waters of the tropics. Surprisingly though, this “dirty” water is responsible for the abundance of marine life found on the North Fork.

Derived from the Greek word planktos, which means wandering or drifting, plankton are organisms at the mercy of the current. They are divided into two groups, phytoplankton and zooplankton, with phytoplankton being one of the most important organisms on the planet.

These single-celled, photosynthetic organisms are primary producers (autotrophs). Like terrestrial plants, they use sunlight and inorganic nutrients to create their own food through the process of photosynthesis.

Not only do they provide nourishment for themselves, they convert otherwise unusable products such as carbon dioxide into invaluable ones such as glucose. This process makes them the base of all aquatic food webs.

Furthermore, an extremely important byproduct of phytoplankton photosynthesis is the production of oxygen. It is believed that between 50 and 80 percent of all the Earth’s oxygen is produced by phytoplankton.

There are four types of phytoplankton: diatoms, dinoflagellates, flagellates and coccolithoporids. Being that sunlight is vital for their survival, it is crucial that they remain in the photic zone of the ocean (a depth at where there is enough light penetration to carry out photosynthesis). Remaining there can be difficult as they are denser than seawater, which will cause them to sink.

To stay near the surface, phytoplankton have evolved several adaptations which make them more buoyant. Diatoms, for example, often have long spines that increase their surface area, in turn slowing the speed at which they sink.  Additionally, individual diatoms will link together to form small chains or even colonies to avoid sinking.

Dinoflagellates have two flagella or simple “tails” that create forward spiraling motion that propel them in the water. Although this mobility is not strong enough for them to swim against the current, it does enable them to migrate vertically in the water column.

Phytoplankton is most abundant in high-latitude locations of the northern and southern hemispheres. During winter months, there is a surplus of nutrients in these regions due to ocean mixing, but sunlight is limiting. As spring arrives, sunlight once again warms these surface waters and plankton populations quickly bloom to take advantage of the bounty of nutrients. By the end of summer these nutrients have become depleted and phytoplankton populations will crash, not returning until next spring.

As I previously mentioned, phytoplankton are one of the most important organisms on the planet, but could there be too much of a good thing? In recent years we are seeing a dramatic increase in the amount of harmful algal blooms (HABs).

HABs are conditions in which phytoplankton populations bloom to such high densities that they have a negative effect on the surrounding habitat and at times can even create human health hazards.

HABs form when there is an excess of available nutrients. This surplus enters our waterways from inefficient sewage-treatment facilities, groundwater seepage contaminated from home septic systems and through the use of fertilizers.

Brown tide is just one of several HABs that can be found locally. It first appeared on Long Island in the mid 1980s and has devastated eelgrass communities ever since. Blooming to densities that turns the water dark brown, it blocks valuable sunlight from reaching the bay bottom, which causes eelgrass to die. When eelgrass perishes, so do all the organism that depend on that habitat for survival.

On the North Fork, brown tide has been responsible for the crash of the historic Peconic Gold (bay scallops) fishery.

Now that winter is coming to an end, we will to see the driving force behind our local marine ecosystems come to life. Fueled by an increase in the amount of daylight, along with an influx of nutrients from winter mixing and rain/snow/ice melt runoff, phytoplankton populations will naturally begin to flourish.

As their numbers grow, they will feed the next level of the food web — the zooplankton.

With a degree in marine biology from LIU/Southampton, Chris Paparo is the manager of Stony Brook Southampton’s Marine Sciences Center. Additionally, he is a member of the Outdoor Writers Association of America and the NYS Outdoor Writers Association. You can follow him on Facebook and Instagram at @fishguyphotos.

One Comment

  • Excellant article. However, please try to be clearer that no one has shown that brown tide is caused by nitrates from sewer systems or other sources. There is no peer-reviewed or other study that shows any statistically significant causal correlation or any correlation between brown tide and nitrates.