The coral reef is a typical formation of tropical seas and oceans, composed of biogenic underwater rock formations formed and increased by the sedimentation of the calcareous skeletons of corals, polypoid animals belonging to the Anthozoa class, phylum Cnidaria.
For this reason, barriers are one of the most important organisms for biodiversity. When alive, corals are colonies of small animals set in shells of calcium carbonate. Coral heads are made up of accumulations of individual animals called polyps, arranged in different shapes.
Polyps are usually small, but they can range in size from a pinhead to 30 cm (12 in). Corals that build coral reefs or hermetic reefs only live in the photic zone (above 50m), the depth at which sufficient sunlight penetrates the water.
Coral reef ecosystems contain distinct zones that are home to different types of habitats.
Usually, three main areas are recognized: the front reef, the reef ridge, and the back reef (often referred to as the reef lagoon). The three zones are physically and ecologically interconnected. Coral reef life and ocean processes create opportunities for the exchange of seawater, sediment, nutrients, and marine life.
Most coral reefs are found in waters less than 50m deep. Some inhabit tropical continental shelves where fresh, nutrient-rich upwells do not occur, such as the Great Barrier Reef. Others are found in the deep ocean surrounding islands or as atolls, such as in the Maldives.
Coral reefs surrounding islands form when islands sink into the ocean and atolls form when an island sinks below the sea surface. The study: Climate-induced increases in micronutrient availability for coral reef fisheries, published on the One earth, said about this issue: "Climate change is transforming coral reefs, threatening supply of essential dietary micronutrients from small-scale fisheries to tropical coastal communities.
Yet the nutritional value of reef fisheries and climate impacts on micronutrient availability remain unclear, hindering efforts to sustain food and nutrition security. Here, we measure nutrient content in coral reef fishes in Seychelles and show that reef fish are important sources of selenium and zinc and contain levels of calcium, iron, and omega-3 fatty acids comparable with other animal-source foods.
Using experimental fishing, we demonstrate that iron and zinc are enriched in fishes caught on regime-shifted macroalgal habitats, whereas selenium and omega-3 varied among species. We find substantial increases in nutrients available to fisheries over two decades following cor al bleaching, particularly for iron and zinc after macroalgal regime shifts.
Our findings indicate that, if managed sustainably, coral reef fisheries could remain important micronutrient sources along tropical coastlines despite escalating climate impacts. "