Snapshots from WWF’s coral reef survey in Goa
The Grande Island Group off the coast of Goa is home to some lesser studied coral reefs. Over a period of 10 days, the WWF-India Marine Team surveyed over seven square kilometers of patchy coral reefs, looking at fish communities, invertebrate assemblages, coral species diversity, and marine litter. The team found the overlooked and mismanaged reefs harbour much biodiversity, and will benefit from further conservation interventions.
The team also counted and categorised the human-generated trash at each of our sites. We found derelict fishing gear mainly in the form of fishing line, sometimes even with the coral having grown over or around it. Derelict gear stuck on a reef can pose a serious threat to animals living here, especially threatened slow-breeding species such as the groupers that occupy the kind of crevices where derelict gear accumulates. We found very little other trash, as compared to those found during a similar survey here in 2015 – this is thought to be a result of the stricter tourism regulations imposed in 2016, following the results of the 2015 survey.
The Grande Island group, off Goa’s coast along the west coast of India, is a pair of islands, Grande and St. George, located end to end, with a narrow channel in between.
Our team consisted of a mix of divers – marine biologists from the WWF-India marine programme, and consultant coral reef ecologists. We partnered with Dive Goa, a local dive company whose divers, intimately familiar with the place, helped us map the study area and provided equipment support.
We wanted to explore biological diversity and assemblages, quantify substrate cover (such as algae, healthy coral, dead or diseased coral etc.), and count & categorise trash and derelict fishing gear on the reef. We did this through visual scans and counts along transect belts, and using quadrat grids to quantify substrate cover.
Estimating substrate cover was one of our most strenuous tasks, and the one that always caused most of us to run low on air in our tanks! A grid was placed at marked points along the transect belts, and the proportions of different substrates within it were noted. In spite of the apparent damage that some parts of these reefs have suffered from bleaching, disease, bioinvasions, physical breakage, and algae growing over coral, we did find healthy coral to be a significant substrate type, and even the dominant type at some of our sites.
On day one, we descended into water so murky that we could barely see our own fingertips, forcing us to rework the standard methodology we had planned to use. However, the visibility on the following days was kind enough to show us reefs more spectacular than we had imagined.
The reefs in these coastal areas are unlike the reefs you would see on postcards. Living in shallow waters that are cloudy with the sediment emptied here by large rivers, these corals are of a resistant type – a handful of species that are specialists. One of the most prominent corals here is Turbinaria (pictured above), which grows as flat plate-like colonies. At some sites, they are truly extensive, with plates the size of dining tables spread out as far as the eye can see even on a clear day.
A very close view of Turbinaria polyps on a plate-like colony
These patchy reef systems are by no means quiet. Many of the sites we surveyed were bustling with crowds of busy reef fish, like an underwater metropolis. Hordes of red-tooth triggerfish swim around slowly, lone groupers and moray eels quietly lie in their crevices, huge armies of territorial damselfish hover above their patches of turf, and gangs of parrotfish prowl around the reef looking for corals to nibble on.
We even saw some fish for which records at this reef are rare – such as this pair of robust Ghost Pipefish, mimicking algae.
We also surveyed the ground in our transect belts for invertebrates. We found a huge diversity of them – far too many to list here. Since an exhaustive reef invertebrate survey had not been done here before, we found several species that have been seen by the local divers but had not been documented formally. (Clockwise from top left – Polyclad Flatworm, Phyllidiamarindica Sea Slug, Chromodoris Sea Slug, Serpulid Fan Worm)
We found interesting patterns in sea urchin abundance across the sites, with two popular tourist sites having very high numbers. Sea urchins are important indicators of ecosystem health. They could indicate either the removal of important predators that feed on them, or an abundance of algae that has overpowered the coral substrate at a site (or both, as might be the case at our study site – algal blooms as a result of runoff pollution, and the anecdotally observed decline of large predatory fish on the reefs.)
All in all, we found that these reefs, which have remained largely ignored from the conservation perspective, are in fact very much alive and abuzz with unique assemblages of biodiversity in an equally special reef system. While tourism in the region serves as a livelihood to many, it is also as an eye-opener to marine biodiversity and its conservation. There is little doubt, therefore, that the sustainability of the activities happening here is of utmost importance, and an immediate priority.