Too Much of a Good Thing

I contribute positively to the environment, working to improve natural habitat with hopes that over time, conditions will improve for everyone. I watch what I eat and my diet consists almost entirely of vegetarian elements, with the only exception a sneaky zooplankton that makes its way inside my mouth by chance every now and then. I, dear readers, am an oyster.

As oyster farmers, we try to feed our babies well by ensuring they have a steady flow of clean, phytoplankton-laden water available, providing ample nutrition and ensuring quick growth to market size. If our oysters don’t get the food they need, they will grow more slowly, dragging out the precious months necessary to leave their subsea homes and venture onto a cool bed of cracked ice near your glass of rosé.

Our beloved namesake, Robins Island, as viewed from the north.

So if it’s all about the nüts (as in nutrients), the more plankton the better, right?

Unfortunately, it’s not that simple. In a well-functioning ecosystem, phytoplankton serve themselves up as a vital part of the food chain for animals large (whales) and small (oysters). Over time, however, human activities ranging from flushing the toilet to industrial farming to playing a round of golf have resulted in unnaturally high waterborne nitrogen levels in some estuaries. Since phytoplankton require nitrogen to photosynthesize and reproduce, more nitrogen equals more plankton under certain conditions.

Nitrogen, in many forms, is essential to our daily lives. Nitrate (NO3-) fertilizer plays a huge (too huge) role in modern farming, nitroglycerin (NG) is used medically as a vasodilator, and nitrous oxide (N20) helps Vin Diesel win races in The Fast and Furious. At normal levels, nitrogen in seawater spurs healthy aquatic plant and algae growth.

However, if nitrogen inputs increase beyond stable levels, we tend to see an explosion of microscopic flora – some of the very same phytoplankton that in the right amounts are essential to shellfish health. Generally speaking, explosive growth of algae and phytoplankton can lead to undesirable ecological outcomes including eutrophication, harmful algal blooms, fish kills, disappearance of seagrass, and loss of marsh habitats

These nutrient loading problems plague portions of mighty estuaries seasonally including the Chesapeake, Long Island Sound, and Long Island’s Great South Bay.

West Robins Oyster Company is located just to the West of Robins Island, in the Great Peconic Bay, a body of water that The Nature Conservancy calls one of the “last great places in the Western Hemisphere,” and we’d have to agree. Our particular plot of water experiences two thorough tidal flushes daily and is certified by the State of New York as a clean and healthy place to grow shellfish.

That said, West Robins stands with groups like TNC, the Peconic Estuary Program and the Peconic Baykeeper in their efforts to measure, analyze and improve water quality over time in the Bay.

A vital precondition of protecting and improving the water quality of the Peconic Bay is an understanding of the local sources of nutrient loading. This 2014 paper takes a high resolution look at three factors contributing to nitrogen loading in the Peconic Estuary including wastewater treatment, fertilizer use, and atmospheric deposition. One of the tricks in conducting such an analysis is determining the spatial extent to which the study should look for nitrogen inputs (check out the perimeter they settled on below).

Using groundwater elevation maps, researchers constructed this Peconic Estuary groundwater contribution map.  All surface and subterranean liquids within the yellow perimeter will take a downhill path toward the Peconic Bay, whereas liquids beyond this perimeter will flow to either the South Shore or Long Island Sound to the north.

The study ultimately determined that 49.6% of the total nitrogen load came from wastewater inputs, which included groundwater leaching from household septic tanks and cesspools (43.0%) and wastewater treatment plants (6.6%).  Next, 26.4% of the nitrogen load could be explained by fertilizers from agriculture, lawns and golf courses. Finally, atmospheric deposition (nitrogen making its way into the estuary via natural processes) accounted for 24.0% of nitrogen loading.

In the map below, pie charts show the specific breakdown of nitrogen inputs at a sub-watershed scale, giving us an intriguing high-resolution picture of how nitrogen loading is distributed across the East End.  Most of the nitrogen load originating from the North Fork comes from fertilizer use, as we’d expect from the large number of vineyards and farms. Nitrogen load originating from the more densely populated South Fork mostly comes from residential septic systems.

Agriculture is responsible for most NoFo nitrogen load, while septics rule the Hamptons. Source: The Nature Conservancy.

Reducing seasonal nitrogen load over time is a complex, multi-faceted dance of prevention and mitigation. The low-hanging fruit of prevention includes tasks addressing point sources such as the Riverhead Treatment Plant upgrades completed in September 2016. Longer term prevention initiatives include smarter agricultural fertilizer application practices and septic system upgrades.

On the mitigation front, time and tidal flushing probably give us the most bang for the buck. However, as oyster farmers, we would be remiss not to mention the ecosystem services we provide. Oysters do their small part to combat excess nutrient load by converting some nutrients to animal and shell mass and through denitrification that releases harmless nitrogen gas to reenter the atmosphere.

At the intersection of academia and the oyster biz, folks are trying to determine to what extent oysters may be an environmental (and policy) tool to rid East Coast estuaries of excess nutrients and restore natural balance. Initial takeaways are that oyster impacts are positive but the magnitude of restorative effects should be measured against the nutrient inputs.

While oyster aquaculture isn’t a panacea for water quality woes, it’s wildly beneficial to the health of the Peconic Bay Estuary and therefore something we can all feel good about in conjunction with other efforts of informed environmentalism.

When you eat an oyster from West Robins, it’s safe to say you just left the Great Peconic Bay a little better than you found it, so eat up & enjoy. We’re proud of you for the decision you made.