A Conceptual Approach towards Utilization of Technological Advancement for Coral Reef Conservation at India

Corals are found to be the ancient marine organisms, and they evolved 540 million years ago [1]. It is sensitive to light, and temperature levels, as well as corals, survived numerous mass extinction events in geological past [2-4]. Coral reefs are home for 25% of marine species and occupy less than 1% of the world’s oceans, form a unique biodiversity reserve [5, 6]. This exceptional biodiversity has Net Primary Productivity (NPP) of 2500g C/ m2/ year [7] and higher than tropical rainforest of 2200g C/m2/year [6] deserves conservation efforts. Its service to our planet earth has been classified in to four major heads regulating, provisional, cultural and supporting services. The regulating services includes carbon sequestration, ocean water filtration followed by provisioning of fish/shell fish protein for humans, jobs through fishing, building materials, medical and genetic research products. The cultural services includes Tourism, recreation, aesthetics to coast and supporting services like coastal erosion prevention and serves as nursery for fish juvenile continually maintaining fish stock. It is predicted that more than 75% worldwide coral reefs were under threat hence; a conceptual approach towards adopting modern technology for coral reef conservation has been studied.


Introduction
Corals are found to be the ancient marine organisms, and they evolved 540 million years ago [1]. It is sensitive to light, and temperature levels, as well as corals, survived numerous mass extinction events in geological past [2][3][4]. Coral reefs are home for 25% of marine species and occupy less than 1% of the world's oceans, form a unique biodiversity reserve [5,6]. This exceptional biodiversity has Net Primary Productivity (NPP) of 2500g C/ m 2 / year [7] and higher than tropical rainforest of 2200g C/m 2 /year [6] deserves conservation efforts. Its service to our planet earth has been classified in to four major heads regulating, provisional, cultural and supporting services. The regulating services includes carbon sequestration, ocean water filtration followed by provisioning of fish/shell fish protein for humans, jobs through fishing, building materials, medical and genetic research products. The cultural services includes Tourism, recreation, aesthetics to coast and supporting services like coastal erosion prevention and serves as nursery for fish juvenile continually maintaining fish stock. It is predicted that more than 75% worldwide coral reefs were under threat hence; a conceptual approach towards adopting modern technology for coral reef conservation has been studied.
Paling of coral due to partial bleaching Change in coral colour arising from changes in the density of zooxanthellae and photosynthetic pigments Darkening of coral in response to reduced light due to photoacclimation Bleaching Considerable whitening of corals due to the expulsion of a large proportion of zooxanthellae from the colony Injury to coral tissue, loss of polyps and partial mortality of the colony Decrease in (live) coral cover

Not Known
Injury to coral tissue, loss of polyps and partial mortality of the colony Decrease in (live) coral cover Partial mortality Mortality Mortality of small-sized colonies and partial mortality of large corals Mortality of susceptible species and size classes Decreased density, diversity and coral cover Decreased density ,diversity and coral cover Changes in community structure Changes in community structure Wide-spread mortality of corals Wide-spread mortality of corals Major decreases in density, diversity and coral cover Major decreases in density, diversity and coral cover Dramatic changes in community structure ,and shifts towards the dominance of non-coral species, such as sponges and algae Dramatic changes in community structure, and shifts towards the dominance of non-coral species, such as sponges and algae However, the sensitivity of a coral reef to dredging impacts and its resilience depends on the ambient conditions habitually experienced. To understand the background concentrations of sedimentation among undisturbed reef environments were studied by [20,21] it mean value ranges from less than 1 to about 110mg cm -2 d -1 or <10 mg L -1 of suspended sediment concentration. In India, sedimentation rate studies are limited, and the pristine reefs of Lakshadweep islands recorded 2.69 to 124.49mgcm -2 d -1 [21]. The highest value was related to monsoonal effects of terrigenous runoff [15]. The data from Palk Bay during May to October 2004 varied between 1 to 42mgcm -2 d -1 [18]. The highest value was recorded during June 2004 heavy precipitation period. However extreme event like a tsunami of 26 December 2004 has elevated the sedimentation rate to 54mgcm -2 d -1 in the Palkbay area [22].  However, the background concentration derived by Caroline [60] found to be suitable for the earlier studies of at Palk bay & Lakshadweep recorded minimum of 1to 2.69mg cm -2 d -1 during the fair-weather periods. Investigations on effects of sediment stress in 89 coral species provided a generic understanding of tolerance levels, response mechanisms, adaptations and threshold levels of corals to the effects of natural and anthropogenic sediment disturbances Paul et al. [19]. The algal symbionts of coral polyps undergo stress from high suspended sediment concentrations and the subsequent effects on light attenuation. The bare minimum light requirements of corals reef ranges from <1% to as much as 60% of surface irradiance Paul et al. [19]. However, the chronic levels of suspended sediment load range between <10mg L -1 in pristine offshore reef areas to >100mg L -1 in marginal near shore reefs Paul et al. [19]. But the tolerance level of exogenous sedimentation rates for different corals species ranged between <10mg cm -2 d -1 to >400mg cm -2 d -1 . The exposure duration of high sedimentation rates varied from<24 h for sensitive species to a few weeks (>4 weeks of high sedimentation or >14 days complete burial) for very tolerant species. This quantification of sensitivity between different coral species was accounted by the growth form of coral colonies and the size of the coral polyp or calyx. These observations were derived from the 77 published studies on the effects of turbidity and sedimentation on 89 coral species Paul et al.
[19] and presented in tabular from [ Table 4 & 5] . Most of the case studies depict discrete turbidity or sedimentation events which produce stress on coral reefs [21]. In India, existing knowledge indicates that inshore corals in certain regions like Gulf of Kutch region may have adapted to high turbidity regimes. According to Anthony & Larcombe [61], coral resilience to turbidity might be of rapid replenishment of energy reserves between periods of sublethal turbidity events, interchanging between phototrophic and heterotrophic dependence, rapid rates of photo-acclimation and energy conservation through reduced respiratory and excretory losses. The current record of the occurrence of symbiodinium spp. at Gulf of Kutch express the physiological resilience is also documented Koushik et al. [62]. These stress response of Indian coral reefs necessitates a comprehensive scientific approach towards solving the siltation problem through technological intervention. The precursor for any technological intervention requisite understanding of the different process governing the sedimentation shall be carried out by numerical modelling. The modeling effort has been warranted only to reef environment where the exogenous sedimentation from the natural environment exceeds endogenous sedimentation from the reef itself.

Technological Interventions
In general, standard engineering modeling tool shall be used to quantitatively simulate sediment transport and deposition with in a system [109]. Hence, conceptual site specific modelling for various sites in India needs to be developed to understand dynamic sediment transport along coral reef systems. As coral reefs have a unique environment, comprehensive understandings of the physical, chemical and biological processes influencing the fate and transport of sediments laden with contaminants of potential concern from sources to exposure media (ie. coral reefs). Hence, a conceptual numerical model shall be developed comprising vital components like hydrodynamic and sediment transport. These components were adequately described by various processes like terrigenous matter inflow through rivers, tidal forcing, meteorological conditions, sediment size gradation, sediment bed properties, advection, dispersion, aggregation, settling, consolidation, erosion transport in suspension, water quality and particle-to-particle interactions and anthropogenic activities of current as well as historical condition. Accounting all these components a numerical model using Mike21, Delf 3D shall be set up to mimic natural conditions. The dynamics of these components shall be simulated using the numerical modelling and calibrated against observed values. Latter validated against the time series field data set collected in a specific manner as per the model requirement. The model output will be of the scenarios of the current, historical and future condition of sedimentation in a reef environment under consideration. The output of the modeling exercise will reveal the impact of siltation due to anthropogenic input (industrial discharge) or other factors like river runoff, bank erosion, etc. If the anthropogenic input predominates the other means of sedimentation, government departments like state pollution control boards and central pollution control boards shall be informed to curb the input through legislative means. However, the exogenous sedimentation rate found to be higher and segregate possible input areas of sediment load shall be mapped within the model domain, and suitable technological intervention may be suggested.
Sediment movement may be arrested by established technologies by providing geotube dykes along the eroding banks to prevent leach outs. As this technology found to be eco friendly and standardized by NIOT for coastal erosion prevention [110]. The model scenario of future condition after technological intervention also been simulated and try to achieve the sedimentation levels of >100mg L -1 or >400mg cm -2 d -1 as reported in the literature. Further studies are required to validate the maximum tolerable level of sedimentation level on coral reefs of Indian coast. The floating macro algal mass settlement on coral reefs of [111] was also reported during January to March. It may be prevented by floating barrier capable of filtering macro algae and not entangle fish as well as turtles. The further large scale is floating algae; garbage netting and collection by [112] may be adopted. This innovative boat capable of collecting floating macro algae materials with its foldable arms covering a width of4m span and collection rate of 98m 3 day -1 during operation. Further, coral reef rehabilitation shall be achieved through Biorock technology which uses mineral accretion process developed by Thomas Goreau, a marine biologist and Wolf Hilbertz, an engineer and architect [113][114][115][116][117] through electro deposition of calcium from sea water enhances the coral growth and the technology found to be viable at certain pockets of world reefs [48,118,119].

Conclusion
Conservation efforts also been achieved through judicial utilization of current technological means.