Production of Particulate Organic Matter by the Reef on Kavaratti Atoll (Laccadives)

Mucus produced by reef corals is a potential energy source for reef organisms. Ingestion and incorporation of mucus aggregates by the gorgonian soft coral Pseudoplexaura porosa was examined using stain and isotope techniques. P. porosa was fed mucus particles stained with neutral red. Virtually all ingested food was cleared from the gut in 3 to 4 h. Gorgonians fed '4C-labelled mucus for 10 min, ingested a mean of 0.91 pg dry weight mucus mg-' gorgonian, and incorporated 22 % of the ingested mucus. The amount of mucus incorporated in these experiments is sufficient to meet the energy needs of P. porosa.

Section: Discussionsupporting

confidence: 61%

Ingestion and incorporation of cora mucus aggregates by a gorgonian soft coral

Coffroth¹

1984

“…Alternatively, it may indicate qualitative differences between detritus in coral reefs and that in other shallow coastal ecosystems. There is evidence that a significant amount of detritus entering coral reef lagoons occurs as organic aggregations derived from fore-reef and reefflat communities (Marshall, 1965;Johannes, 1967;Qasim and Sankaranarayanan, 1970). These amorphous aggregations, consisting largely of coral mucus, flocculated organic substances and adherent particulate matter (Johannes, 1967;Coles and Strathman, 1973) may comprise half of the particulate organic carbon found in lagoonal waters; the remainder appears to be principally of algal origin (Marshal1 et al, 1975).…”

Section: Resultsmentioning

confidence: 99%

Nutrition of Deposit-Feeding Holothuroids and Echinoids (Echinodermata) from a Shallow Reef Lagoon, Discovery Bay, Jamaica

Hammond¹

1983

Concentrations of organic carbon and nitrogen, ATP, and total plant pigment (chlorophyll a + phaeophytin) were approximately twice as high i n foregut contents of the deposit-feeding, aspidochirote holothuroids Isostichopus badionotus Selenka, Holothuria rnexicana Ludwig and H. arenicola Forskal, and spatangoid echinoids Meoma ventricosa Lamarck and Plagiobrissus grandis Gmelin than in the adjacent sediments. This suggests that holothuroids and spatangoids selectively ingest nutrient-rich grains, contrary to the conventional view that they show poor chemical discrimination. The availability of the organic food resources did not vary consistently between different grainsize fractions of sediment. This obviates any a priori expectation that discrimination on the basis of grain quality, demonstrated here, will be coupled to discrimination according to grain size, previously shown not to occur in these species. Assimilation efficiency of the ingested carbon averaged 42 %. Plant carbon, calculated from pigment concentrations and probably derived from diatoms, represented a major carbon resource in the available sediments, but only a small proportion of that ingested was apparently assimilated. Meiofauna, a minor component of the available carbon (ca. 1 %), were ingested in lower numbers than those at which they occurred in the sediment, and were not digested or assimilated. Bacterial biomass was not determined, but other studies suggest that its contribution to the sedimentary carbon pool is low. It is likely that at least half of the carbon assimilated by these deposit feeders is of detrital origin. This result, which contrasts with present understanding of the nutrition of deposit feeders, may be indicative of qualitative differences between detritus of coral reefs and that of other shallow, coastal ecosystems.

“…19921 but only 05'% of t h~s amount = 88.4 pg C 1.' is expected on the shallow reef slope which is relatively more ~nfluenced by incoming oceanic water (Marshall 1968, Qasim & Sankaranarayanan 1970, Hatcher 1983b. Of this, 16"A is <2 pm and : .…”

Section: Carbon Flux In the Algae-dominated Statementioning

confidence: 99%

Carbon flux on coral reefs:effects of large shifts in community structure

Johnson¹,

Klumpp²,

Field³

et al. 1995

The effect of replacement of live coral cover by epilithic algae on patterns and magnitudes of carbon flux is examined for the shallow front slope of a midshelf reef in the Great Barrier Reef (GBR) complex of Australia. A steady-state network of carbon exchange among 19 trophic compartments is constructed for the coral-dominated state. From this, 2 scenarios for patterns of carbon flux when algae dominate are derived, viz.(1) the increase in algal production is channeled to detrital pathways (grazers do not respond), and (2) grazers utilise the increase in production of algal carbon so that transfers to detritus and grazers are in the same proportion as occurs when coral cover is high. The 3 models summarise current knowledge of carbon flux on GBR reef fronts and are compared using network analysis. Because fluxes in the reef front zone are dominated by exogenous imports and exports as a result of the high volume of water passing around and over the reef, the analyses ignore advective fluxes across the zone that are not internalised.The shift in structure to an algae-dominated system realises lower rates of benthic primary production, and thus system slze and activity (i.e. total system throughput, internal throughput, development capacity and ascendancy) are reduced, suggesting a disturbed system. With loss of coral cover, the proportion of the total flow that is recycled and transferred to the detritus pool increases (although the structure of recycling is not affected), and the balance of pathways in the network is changed: average path length increases, while the average trophic level of most of the second order consumers, and trophic efiiciencies of most trophic categories, decreases. Also, there are marked changes in dependencies of particular trophic groups on others. The analysis shows that, in the coral-dominated state, carbon fixed by zooxanthellae is used indirectly by most organisms in the system, even those seemingly remotely connected. Differences between the coral-and algae-dominated systems were much greater than differences between the 2 scenarios for the algae-dominated state. However, the exact fate of additional algae-derived carbon In the system is an important consideration since the 2 scenarios for the algae-dominated state yielded dissimilar values for some parameters (e.g. flow diversity, trophic dependencies and effective trophic levels of some compartments, relative importance of recycling, trophic efficiency of some trophic categories).