Changes in the marine environment: Pacific oyster threat as waters warm
Warming seas have allowed a boom in numbers of non-native Pacific oysters, threatening to change ecosystems in important estuaries of the south west. Pacific oysters were introduced to the UK in the 1920s, and then commercial oyster farms were established in the 1950s and 1960s, it was believed that they wouldn’t breed because our waters were too cold. Recently, though, the oysters have spread beyond the farms and trained citizen scientists from Cornwall Wildlife Trust’s Shoresearch Project, along with other partners, are mapping the oyster explosion. In Cornwall the Tamar, Fowey, Fal and Helford estuaries are now heavily inundated with Pacific oysters. Solid Pacific oyster reefs are forming in some areas which are changing the ecosystem and smothering intertidal gravel and mudflats, making it difficult for birds and young fish such as bass and mullet, to forage on these rich and important feeding grounds. Some areas have recorded up to 200 oysters per square metre.
Healthy seas are essential for wildlife and are also a key part of tackling climate change. Oceans are the largest sink for man-made carbon dioxide, and it’s estimated they absorb between 20% and 35% man-made CO2 each year
Matt Slater, marine awareness officer, Cornwall Wildlife Trust says:
“Originally, Pacific oyster famers were officially advised that our waters weren’t warm enough for them to reproduce, but due to climate change that advice is out of date. Pacific oyster populations have increased hugely in Cornwall and Devon in the last five years and it’s unrealistic to think we’ll be able to eradicate this species, so we’re going to have to manage them the best we can. There are big feral populations on the coasts of Kent and Essex too. This is a cautionary tale, showing the unforeseen consequences of introducing new species, and particularly the effect a changing climate is having on marine ecosystems.”
Action for marine conservation: Seagrass & saltmarsh restoration – great for wildlife, good for carbon storage; endangered skate and sharks successfully tracked; native oyster reintroduction; over 5000 marine volunteers; Fishing 4 Litter cleans-up 27 tonnes of marine waste, and a milestone – 41 new Marine Conservation Zones announced
This year Alderney Wildlife Trust donated seeds from their underwater seagrass meadows at Longis nature reserve for an innovative project planting a new meadow off the Welsh coast. Seagrass stores about twice as much carbon per hectare as terrestrial soils. Alderney’s seagrass tolerates warmer waters and the Trust sustainably harvested seeds for Swansea University to germinate, before being transferred to small hessian bags to be planted underwater.
UK saltmarsh has declined by 85% in the past 100 years and what is left needs emergency protection. Saltmarsh captures large amounts of carbon through photosynthesis, storing the carbon in its vegetation, and the deep sediment beneath the surface. Saltmarshes also protect coastal land against flooding as a result of storm surges. Essex Wildlife Trust notched up a number of firsts this year with successful surveys showing fish are now colonising an emerging area of saltmarsh at Fingringhoe Wick, created following a planned breach in the sea wall five years ago. A new expanse of channels, lagoons and marsh is already becoming an important place for fish, waders and wildfowl. The first winter fish survey found new species like thin lipped grey mullet are using the saltmarsh. At Abbots Hall Farm the first year of monitoring showed success for coir rolls installed by the Trust to protect the marsh, and for the first time citizen scientists trained by the Trust discovered numerous young fish including gobies, shrimp, bass, sea gooseberries, a small iridescent jellyfish at Two Tree Island saltmarsh.
Joan Edwards, The Wildlife Trusts’ director of living seas, says
“Healthy seas are essential for wildlife and are also a key part of tackling climate change. Oceans are the largest sink for man-made carbon dioxide, and it’s estimated they absorb between 20% and 35% man-made CO2 each year. We need to protect and restore blue carbon habitats such as seagrass meadows and saltmarshes as one of our most effective and natural solutions to the climate emergency.”
Ulster Wildlife reported a great year for the critically endangered common skate, (also known as flapper skate) which can live for up 100 years and grow to three metres long. Working with local sea anglers through the SeaDeep project, fish were tagged and monitored.
Rebecca Hunter, Ulster Wildlife’s living seas manager, says:
“Skate grow very slowly so it can take decades for populations to recover. We offered sea anglers free training and equipment, showing them the best way to handle and tag fish with a unique number, at the same time as measuring them and giving a condition check, before quickly returning them to the water. Anglers also helped tag spurdog sharks which can live to 70 years and are endangered in Northern Ireland. Their enthusiasm for helping us save these species has been fantastic and over 200 sharks, skates and rays have been tagged so we can monitor numbers and condition.”
Native oysters were re-introduced to the Humber estuary for the first time since the 1950s. Working in partnership with University of Hull, Yorkshire Wildlife Trust reintroduced the oysters in a sheltered area at Spurn Point nature reserve where students will be able to monitor growth, water quality, and marine wildlife. Oysters are nature’s water filters and help clean pollution from estuaries and seas.
This year coastal Wildlife Trusts were supported by over 5000 volunteers who took part in beach cleans, citizen science surveys and shore-based events. Trained Shoresearch citizen scientists completed over 95 surveys recording marine creatures and submitting their data to national records centres. Many Wildlife Trusts volunteers stood up for their local coasts: Hampshire Wildlife Trust’s Secrets of the Solent had over 100 people signing up to train and become Marine Champions, while North Wales Wildlife Trust’s Wild Coast had its busiest year with young volunteers racking up an incredible 1,806 individual volunteer hours in the past 12 months – that’s around 2.5 months of continuous, non-stop work to help protect and promote safe havens for nature. Cornwall Wildlife Trust’s Your Shore Beach Rangers inspired young people, Kent Wildlife Trust’s Guardians of the Deep contributed survey data, and Lancashire Wildlife Trust’s 660 students enjoyed Beach School. Devon Wildlife Trust’s Wembury Marine Centre celebrated its 25th anniversary with a 24-hour bioblitz – working with The Marine Biological Association 115 volunteers recorded 1310 species, (610 of which were newly recorded within 10km of Wembury Marine Centre) – all within 24 hours. Most exciting finds were two rare giant goby found during night-time rockpooling.
Legendary volunteer Ray Marsh won The Wildlife Trusts’ Cadbury Medal for services to nature conservation. Ray retired in October after 60 years as volunteer warden of Essex Wildlife Trust’s Skipper’s Island; he rowed across to the island 10,000 times to look after this haven and its wildlife.
Yorkshire Wildlife Trust’s Fishing 4 Litter had its best year with a phenomenal 27 tonnes of litter and fishing gear collected by fishermen and deposited in skips and waste points in eight harbours along the Yorkshire Coast. This project offers 160 fishermen hard-wearing, reusable bags for use at sea which are then emptied ashore – bins and skips are collected by councils in North and East Yorkshire.
This year Wildlife Trusts organised 450 beach cleans, with many more independently-run by volunteers themselves and through local partnerships. Trusts counted rubbish by the bag, tonne and even piece, for example: Sussex Wildlife Trust logged 19,000 pieces of litter weighing 350kg; Scottish Wildlife Trust reached remote island beaches by boat, removing over 5 tonnes of washed-up litter, plastic and fishing gear; and Isles of Scilly Wildlife Trust cleared 2.5 tonnes from their coastline. Plastic eye-drops bottles washed up in Hampshire and Devon, and plastic nozzles covered a beach in Kent.
After almost 298,000 people backed a 7-year campaign by The Wildlife Trusts to protect UK waters, 41 new Marine Conservation Zones were announced this year bringing the total to 91. Citizen science provided the evidence needed to achieve this milestone and it will mean greater marine protection for special underwater places including cold water corals, forests of sea fans, rocky canyons and sandbanks – an astonishingly varied range of submerged landscapes and habitats which support the stunning diversity of marine life found in the UK.
Joan Edwards, The Wildlife Trusts’ director living seas, says:
“The announcement of new Marine Conservation Zones marked a watershed in our battle to protect our seas. We want this small corner of our blue planet to recover and our waters to teem with life once more. Now the government must introduce better management of MCZs and enhance protection for a selection of areas to show how seas can recover when damaging activities are removed.”
In Scotland, proposals to create the world’s first protected area for basking sharks, in the Sea of the Hebrides, were supported by The Scottish Wildlife Trust, which encouraged more than 3000 people to back the plan. Basking sharks congregate to feed on plankton in Hebridean waters from May to October; numbers plummeted in the 1900s due to widespread global hunting.