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Restoring shellfish reefs for people and nature

Shellfish are underappreciated, but crucial animals in marine ecosystems. Shellfish reef restoration has amazing potential help marine ecosystems.
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In this section we’ll talk about one of the most threatened ecosystems in coastal landscapes. That’s the bad news. The good news is that we’ll also be talking about the huge efforts being made around the world to restore them right now. Hi there. My name is Dr. Ben Gilby. I’m a coastal ecologist at the University of the Sunshine Coast, Australia. Do you like to eat oysters, those glistening salty gems of the sea. They’re considered a delicacy all around the world, and are consumed in their millions each day. But these little delicacies are also fundamental to the ecology and health of our coastal landscapes in many parts of the world.
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For example, did you know that a single oyster can filter up to a bathtub of water a day? Oysters are a type of filter feeding bivalves. They filter water and remove plankton, sediment and other nasties from the water column. They also sequester the leftovers into the underlying sediments. This whole process is great for coastal ecosystems because it can really help to clean up coastal water quality and keep other ecosystems like sea grasses alive. Did you know that billions of oysters can come together to form expansive reefs that can be hundreds of metres long. These are often called oyster or shellfish reefs.
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These rape support not only oysters, but hundreds, perhaps 1000s of species of small invertebrates, predatory polychaete worms, algae eating gastropods, and other filter feeders like corals and sponges. oyster reef supports such huge biodiversity. And this means that oysters are classified as keystone species in many coastal seascapes. And did you know that these expensive rates can help support our coastal communities by reducing coastal erosion and supporting our coastal fisheries? Just 10 square metres of oyster reef habitat produces 2.6 kilogrammes of fish per year that we can catch an eight. This is mostly because oyster reefs either enhance the survival of larval fish, or provide habitat with food resources and shelter from predators during early adult stages.
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But there’s a big problem, a huge problem. Globally, Scientists estimate that between 80 and 85% of shellfish reefs have been lost. And this number keeps increasing every year. In some parts of the world, including on the east coast of Australia, up to 96% of oyster reefs are gone. In many systems, they’re considered functionally extinct, which means the important role they play in coastal ecology is entirely gone. We talk a lot about the threats facing coastal landscapes. Humans have urbanised coastlines over harvested coastal fisheries in many regions. This causes substantial damage to all coastal ecosystems, sea grasses, mangroves and coral reefs.
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However, no ecosystem has experienced such a global decline as shellfish rapes, that 85% global loss figure is greater than estimates for all of those other ecosystems. It’s arguable, therefore, that shellfish reefs are the most threatened coastal ecosystem on Earth. declines in their extent and condition are caused by a myriad of impacts. Predominantly, shellfish rates have been lost due to the combined effects of diseases which are often worsened by coastal urbanisation over harvesting for food and limestone, high sediment and nutrient runoff from degraded coastal catchments, or trampling by people who walk through intertidal areas. And this decline in shellfish reef extent and condition is causing significant harm to coastal communities.
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The loss of shellfish reef have been implicated as contributing towards the decline of several key coastal ecosystem services, the things that people gain and benefit from coastal ecosystems. For example, shellfish reef decline has been implicated in contributing towards fisheries declines and coastal erosion all around the world. But here’s the good news. There is something that we can do about this. There is a global movement, which is surging, shellfish reef restoration. All around the world. People are working hard to restore shell fisheries to our coastal landscapes. But to understand how people are doing this, let’s talk a little bit about some simple shellfish biology. Oysters are bivalves, a type of mollusk related to snails.
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However, oysters are a bit different to snails in that they are benthic and sedentary. Once they settle on the sea floor, they simply cannot move. When I stood spawn, they released their sperm and eggs into the water column which makes the eggs hatch into larvae and the larvae swim bouton, seeking out hard surfaces to settle on and grow. This is why we often see oysters growing on jetties and sea walls. One of the most interesting thing is that oyster larvae most like to settle on other oysters. They like to live with their conspecifics attached oyster larvae are called spat and they are usually less than 25 millimetres long. The spat grows into adults and the whole process starts again.
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When shellfish reefs a loss from coastal landscapes, the rocks and other hard substrates that they naturally lived on are either also removed by people or simply erode away by the action of the tides and wind over time. There are no more accurate moist is left in the area, meaning that oyster larvae struggle to find ideal sediment locations. This means that even if there are larval oysters swimming around in the water column, they simply have no place to settle and to continue their lifecycle. So how does all of this relate to shellfish reef restoration? Well, one of the most important aspects of shellfish reef restoration is to reinstate hard substrates to coastal landscapes.
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oyster larvae can then settle on this restored hard substrate grow and commence their lifecycle. There are many different ways in which this hard substrate is being reinstated to coastal landscapes all around the world. Because we know that oyster love I love to settle on other oysters. One of the best ways to restore oyster reefs is to use recycled oyster shells. All around the world. People are collecting tonnes and tonnes of oyster shells from restaurants, oyster bars, oyster shuckers, piling them up in the sun to kill any nasties and then packaging them into biodegradable containers or bags. This is a fascinating process.
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These containers or bags are then placed in coastal environments, usually on unvegetated sands or muds when nature is left to do its work. oyster larvae settle on the recycled oyster shells and grow reproducing resulting in new self sustaining rates and coastal landscapes. In other parts of the world, people are deploying huge volumes of rocks, boulders and reef units. This can result in huge extense hectares and hectares of reefs being restored in a shorter amount of time. This is big industry. This sort of restoration can lead barges and cranes and excavators. This is coastal restoration at a massive scale.
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Many of these projects are driven by communities, shell recycling projects workshops to create and build the reefs themselves, communities working to monitor and grow shellfish all around the world. This community stewardship is a crucial part of coastal restoration people on the ground who are passionate to make the change in their world. oyster reef restoration was pioneered in the Gulf and East Coast of the United States of America. There are hundreds of projects that are now including some of the largest restoration efforts in the world. The desire to restore shellfish reefs has now expanded globally to Europe, Asia and Australia. In Australia, there are dozens of shellfish reef restoration projects.
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One of these Australian projects is in pumicestone passage on the Central Asian Australian coast. This is a project with two hectares of shellfish reef restoration, where six types of reefs were deployed to test which method works best for oysters. Hundreds of oysters are now settling on these reefs per square metre of recycled shell. The most exciting part of this project is the huge fisheries benefits. At pumicestone passage, the diversity of fish at the reef has expanded by fourfold and the abundance of fish that we like to catch and eat has increased by over 16 fold. These benefits are huge, and it is resulting in great recreational fishing opportunities for people right across the region.
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But pumicestone passage is only small, it’s about two hectares about four football fields in size. Imagine what will happen when we expand this effort to even bigger areas across multiple coastal systems, the benefits to ecosystems and people will be huge. All of this ties in beautifully to the United Nations Declaration of the decade 2021 to 2030 as the UN Decade on ecosystem restoration, which aims to prevent halt and reverse the degradation of ecosystems worldwide. Shellfish rates might be just one component of our coastal seascapes, but they are a crucial component and contribute disproportionately to the biodiversity of our coastal ecosystems.
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So next time you sit down to one of those tasty morsels of the sea, think about how this little critter helps coastal biodiversity to protect our coastal assets and to enhance our coastal fisheries. From little things big things grow

Shellfish, like oysters, are considered delicacies all around the world. People love them for their salty taste. Shellfish are also crucial for our coastal ecosystems because they filter water and create reefs that provide homes to hundreds, if not thousands, of coastal species. They also support significant fisheries which feed coastal communities.

In this video we discuss shellfish reef restoration- the act of reinstating shellfish reefs to coastal seascapes. We delve into the benefits that this restoration effort has for coastal biodiversity, fisheries, and the economies of coastal towns.

From little things, big things grow.

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Life Below Water: Conservation, Current Issues, Possible Solutions

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