oceany: Sea cucumber

Evidence: 100 • authority: 72

Sea cucumbers are echinoderms from the class Holothuroidea ( HOL-ə-thyuu-ROY-dee-ə, HOH-lə-). They are benthic marine animals found on the sea floor worldwide, and the number of known holothuroid species worldwide is about 1,786, with the greatest number being in the Asia–Pacific region. Sea cucumbers serve a useful role in the marine ecosystem as detritivores who help recycle nutrients, breaking down detritus and other organic matter, after which microbes can continue the decomposition process. Sea cucumbers have a leathery skin and an elongated body containing a single, branched gonad; they are named for their overall resemblance to the fruit of the cucumber plant. Like all echinoderms, s…

Evidence: 54 • authority: 72

In biology, detritus ( or ) is organic matter made up of the decomposing remains of organisms and plant material, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decompose (remineralise) it. Such microorganisms may be decomposers, detritivores, or coprophages. In terrestrial ecosystems detritus is present as plant litter and other organic matter that is intermixed with soil, known as soil organic matter. The detritus of freshwater ecosystems are mostly leaf litter and other decaying organic materials. These are decomposed by microbes, and small invertebrates that shred leaves or filter feed suspended organic matter. The detritus of marine ecosystems…

Evidence: 49 • authority: 90

Sea cucumbers, classified as Holothuroidea within the phylum Echinodermata, are large and abundant members in marine benthic communities 1 . Sea cucumbers greatly impact the health and integrity of the marine ecosystem through bioturbation, organic matter processing, nutrient recycling, seawater chemistry balancing, biodiversity supporting, energy transfer in food chains 1 , 2 , and provide significant protective benefits to coral reefs by reducing their diseases 3 . Most sea cucumbers are deposit feeders, acquiring nutrients through the consumption of bacteria, microalgae, decayed plants, and meiofauna, along with other organic detritus 4 , 5 , 6 . By ingesting and defecating a large amount of seabed sediment, sea cucumbers facilitate bacterial decomposition and reduce the organic load 4 , 7 . To date, the specific mechanisms by which sea cucumbers obtain sufficient nutrition from the marine benthic deposit remain unclear. Marine animals acquire nutrition through different feeding modes, including herbivory (e.g. sea urchin) 29 , carnivory (e.g. starfish) 30 , filter feeding (e.g. oyster) 31 , symbiotic nutrition (e.g. coral and giant clam) 32 and deposit feeding. The process of deposit feeding involves ingesting large amounts of sediment to obtain organic matter. Deposit feeders are not common in the marine benthic community, except for polychaete annelids (e.g. Nereis succinea ) 33 , sipunculids (e.g. Sipunculus nudus ) and echiuroids (e.g. Urechis unicinctus ) 34 , while sea cucumbers are among the most significant groups. Organic matters in the shallow seabed sediments mainly consist of the remains of dead animals and plants, as well as sediment-attached microalgae, bacteria and fungi 35 . However, the organic matter content in the seabed substrate is relatively low, therefore, sea cucumbers need to ingest large quantities of sediment to obtain sufficient nutrients for survival, growth and reproduction 1 . Although sea cucumbers inhabit a broad geographic expanse globally and their living environments vary with the climate, most are shallow-water deposit feeders. The repertoire of digestive enzyme genes in their genomes remains evolutionarily conserved, whereas their diets and gut microbial communities may exhibit variation due to environmental differences. This study reveals the evolutionary innovations of sea cucumbers for adapting to the deposit-feeding style, including the expansion of the digestive carbohydrase gene repertoire, contraction of digestive protease gene repertoire, and the occurrence of intestinal i-type lysozyme genes in their genomes. The changes in the expression patterns of digestive enzymes accompanying the dietary shifts during the sea cucumber development are also elucidated. This study further demonstrates relationships between the gut microbiota and the digestion process in sea cucumbers, namely, some resident bacteria provide digestive enzymes, while others are digested by intestinal lysozymes to serve as a food source. Our study may provide insights into the mechanisms by which sea cucumbers effectively utilize nutrients from seabed sediments in marine ecosystems.

Evidence: 49 • authority: 90

Feces in Aquatic Ecosystems. Think of trophic levels, and what probably comes to mind is an illustration from a biology text showing a pyramid, with solar energy trapped by photosynthesizing plants on the bottom, plants fed upon by herbivores in the middle, and herbivores eaten by carnivores on top. These models may also show arrows indicating that feces and dead plants and animal bodies provide inputs to the detritus pool, illustrating how this organic matter is recycled by microorganisms, and how at all trophic levels, aerobic respiration results in the loss of energy from the ecosystem. Such conceptual models provide a basis for energy budgets to be investigated, but the focus of early s…

Evidence: 49 • authority: 90

A Review of Factors Influencing the Seagrass-Sea Cucumber Association in Tropical Seagrass Meadows. In the tropical ecosystem, sea cucumbers are associated with seagrass meadows in various ways, often forming a network of ecological interactions. From this myriad of interactions, the trophic relationship between the seagrasses and sea cucumbers has received recent attention with the advent of analytical techniques. However, little is understood about the exact mechanism by which seagrasses are sustaining the sea cucumber populations in the food chain, considering the high number of refractory components in seagrasses and the lack of digestive enzymes among sea cucumbers. This manuscript aim…

Evidence: 44 • authority: 72

A coral reef is an underwater ecosystem characterized by reef-building corals. Reefs are formed of colonies of coral polyps held together by calcium carbonate. Most coral reefs are built from stony corals, whose polyps cluster in groups. Coral belongs to the class Anthozoa in the animal phylum Cnidaria, which includes sea anemones and jellyfish. Unlike sea anemones, corals secrete hard carbonate exoskeletons that support and protect the coral. Most reefs grow best in warm, shallow, clear, sunny, and agitated water. Coral reefs first appeared 485 million years ago, at the dawn of the Early Ordovician, displacing the microbial and sponge reefs of the Cambrian. Sometimes called rainforests of…

Evidence: 39 • authority: 80

Peer Review #3 of "Sea cucumbers reduce chromophoric dissolved organic matter in aquaculture tanks (v0.1)"

Evidence: 39 • authority: 80

Role of sea cucumbers as an ecosystem service in land-based aquaculture

Evidence: 34 • authority: 69

Bioturbators enhance ecosystem functioning in marine sediments by modifying geochemical gradients, redistributing food resources [1] , and altering nutrient fluxes. All of these factors influence coastal productivity [2] . Accordingly, the net effect of bioturbators on sediment biogeochemical processes is often markedly different from that predicted by simple linear food-chain theory [1] . Yet predicting ecosystem-level effects of these ‘ecosystem engineers’ can be challenging owing to multiple feedbacks and emergent properties [3] , [4] . Accordingly, the potential consequences of losing these important functional groups from overfishing [5] or physical disturbance of the benthos [6] has ramifications for ocean ecosystems and human well-being. Global invertebrate catches have increased six-fold since 1950 [5] , with overfishing causing population declines in 81% of sea cucumber fisheries [5] , a ubiquitous and functionally important group of bioturbators [1] . Given their important role as bioturbators, it has been suggested that the presence of deposit-feeding sea cucumbers can reduce the accumulation of excess organic matter in coastal sediments such as under aquaculture farms [7] , [8] . Furthermore, incorporating sea cucumbers into the aquaculture of finfish or bivalves may reduce pressure on overexploited wild populations and add another valuable farmed resource. Integrated multitrophic aquaculture (IMTA), whereby farm nutrients and organic particulates are recycled through the co-culture of species from different trophic levels, has been proposed to reduce production costs and minimize deleterious ecological effects of aquaculture [15] . However, in spite of research into fish–bivalve–seaweed combinations [16] , the potential role of bioturbating benthic organisms in IMTA systems has received only limited attention. Deposit-feeding sea cucumbers reduce the accumulation of organic carbon under mussel farms [8] and thus show promise as a management tool; however the complexity of ecosystem functions performed by sea cucumbers demands a better understanding of their interactions with sediment biogeochemistry and benthic-pelagic coupling. Most sea cucumbers are omnivorous deposit-feeders that not only compete with, but also feed directly upon, benthic bacteria [17] . Traditional food web models predict that bacteria, as the intermediate consumer, will eventually be excluded in such omnivorous associations [18] . However, the importance of positive interactions/facilitation [19] and scale niche differentiation [20] demonstrate that these traditional models have overlooked complex interactions among species. The stimulatory effects of sediment infauna on bacteria (e.g., increased O 2 supply and release of reduced metabolites) are well understood [21] and may also be relevant to epibenthic organisms such as sea cucumbers. Moreover, by consuming and reconstituting large quantities of sediment, deposit-feeding sea cucumbers may create favorable conditions for bacterial activity [22] . Sediment feeding sea cucumbers also elevate nutrient concentrations through excretion [23] , while bioturbation by burrowing Echinocardium can enhance nutrient efflux from the sediments [2] . The elevated nutrients in turn improve conditions for sediment primary producers, notably microphytobenthos (MPB) [2] , [24] . However, deposit-feeding sea cucumbers also graze and through bioturbation can disturb MPB communities [25] . Moreover, positive and negative interactions can be dynamic, varying in their relative strength along environmental gradients [26] . The balance between organic matter (OM) remineralization by bacteria and nutrient assimilation by primary producers determines the rate of benthic-pelagic nutrient exchange and organic matter content in marine sediments [27] . Thus, the effect of bioturbation on microbial producers and decomposers has important consequences for the potential of sea cucumbers to ameliorate the effects of eutrophication.

Evidence: 0 • authority: 69