Cuan Beo Environmental tells us how oysters can teach us how our land based activities effect the marine environment

Untold wonders of the watery world, ecological processes of incredibly intricate design,  systematic environmental catastrophes unfolding over time and genius nature based  solutions to our impending doom owing to an environmental disaster of our own making –  all can be revealed to you by an oyster – but first you have to learn how to listen to them!

Communication with an oyster is certainly difficult. He is a faceless, noiseless, voiceless  molluscan bivalve that generally lives under a couple of million of gallons of water, so to plainly ask him ‘Mr Oyster, are there any land based water pollution pressures directly  affecting your habitat?’ will most likely leave you without a satisfactory response and  understandably frustrated. But maybe the oyster is answering us and we just have to  change how we listen!

If we observe the oyster over time, examine how he is interacting with his environment,  examine what he is eating, examine how he is reproducing and consider the water he is  living in and how this water is delivered to his environment, we’ll begin to uncover  tangible connections between land land and sea, and understand through the changes  observed in the oyster’s behaviour how our land based water management activities  directly impact the marine ecosystem and marine biodiversity. 

There is significant pressure placed on our coastal environment owing to the actions we  take on land. Storm water overflows, agricultural run off, urban waste water, land drainage  ,surface water overflows or sewage treatment all present a significant environmental  challenge to marine life when they are discharged either directly or via a fresh water  inputs (river, stream, groundwater) into the marine environment. These discharges can  result in huge mortalities in marine life or substantial habitat lost owing to a number of  detrimental habitat alterations such as increased sedimentation, increased eutrophication,  direct pollution via harmful substances or substantial reductions in salinity concentrations  and temperature ranges owning to increased fresh water land drainage. 

There is sometimes a misconceived belief that the ocean is so vast that it can withstand  these pressures and that the majority of land based pollutants are diluted into the open  Atlantic – the opposite is in fact the reality! There are ‘invisible’ boundaries in the ocean,  created by a number of different factors including tides, areas where fresh and salt water  meet, currents, areas of different depth or temperature, and many others, that effectively  retain water in a the immediate coastal environment. This means that land based  discharges do remain in the immediate coastal coastal environment for a significant  period of time and present a risk to marine life or result in habitat loss for a number of  marine species.  

Studying marine life like the oyster, trying to understand his decline in population, his  increased mortalities or poor reproduction and settlement allows us to quantify the impact  of these land based water pollution activities and understand how our actions can directly impact multiple ecosystems – unfortunately, studying oysters usually reveals how we are  acting to their detriment! 

However, it is not all doom – luckily the oyster is an optimist, and just as often as he tells  us we have done something wrong he rewards us when we do something right! When we  improve a fresh water input into the marine environment this almost immediately translate  to an improvement in oyster survival and marine biodiversity in general. If we reduce  nutrient enrichment by planting buffer zones on land this results in healthier algae  populations for oysters to graze on, if we reduce sedimentation by installing siltation traps  on rivers and streams and allowing them to flood and meander naturally this creates more  ‘clean’ habitats for new oysters to settle on, and if we retain more water on land through  wetlands, surface water capture and rain water capture this eliminates large drops in  marine salinity concentrations owing to substantial fresh water discharges.

The water biodiversity training provided by Veri Connect to community groups is invaluable in  demonstrating how we can improve our land based water management and achieve large  scale environmental restoration through actions as simple as installing rain water  harvesters, digging a pond or leaving some land for floods. The right action in the right  place can go a long way – and we don’t need to prove it, the oysters will do that! 

Many thanks to Alec Reid who is the Oyster Reef Restoration Officer at Cuan Beo Evironmental Clg, Galway Bay for this guest post. We were privileged to hear Alec speak at a Networking Event for Galway Rural Development, his passion and knowledge in his field of expertise had everyone in the room captivated.