Mumbai: Is marine life vanishing amid city's rapid transformation?

An old photo of Menella indica, a species of octocoral that was missing during researchers’ recent trip. Pics/Pradip Patade

The area around the rocky outcrop off Chowpatty where the Chhatrapati Shivaji Maharaj Memorial is to be built has undergone alarming ecological changes over less than a decade, according to a recent biodiversity survey. The researchers suspect a combination of human-driven and natural causes, including coastal development and climate change, are primarily to blame.

Pseudopterogorgia fredericki, or the Indian Sea plume, a species common along Mumbai's rocky shores. Pics/Pradip Patade

Located 1.07 to 1.5 nautical miles, or 1.9 to 2.7 km, off Chowpatty, the site was once a thriving underwater habitat, rich with corals, gorgonians, nudibranchs, gastropods and reef fishes. In the last week of May, marine biologist Dr Ramvilas Ghosh and Pradip Patade, co-founder of Marine Life of Mumbai and director of the Coastal Conservation Foundation (CCF), visited the proposed memorial site during low tide and conducted a two-hour-long survey. Following the visit, both experts revealed ecological changes that point to the possible local extinction of key marine species.

The experts told mid-day that several sessile (immobile) colonial organisms have vanished entirely from the site, which is an offshore extension of the rocky coastal ecosystem of South Mumbai. "The disappearance of gorgonians, especially Menella indica and Echinogorgia sp, is not just a loss of individual species; it signals a collapse in the ecological balance of the entire system," said Dr Ghosh, whose conservation efforts are supported by the Mohammed Bin Zayed Species Conservation Fund.

What are gorgonians?

Gorgonians, also called sea whips or sea fans, are a type of marine invertebrate commonly known as octocorals and are found along the coast of Mumbai in intertidal and subtidal zones, which are coastal ecosystems that lie between the high and low tide marks.

Genus Echinogorgia, commonly known as spiny sea fans, at the spot where the proposed Chhatrapati Shivaji Maharaj Memorial is slated to be built

The survey also formed part of CCF's citizen science project Marine Life of Mumbai, led by Patade. From April to May 2025, the duo conducted surveys across several key sites, from Geeta Nagar in Colaba, the stretch from Nepean Road to Haji Ali and Carter Road in Bandra West, covering significant portions of Back Bay and South Mumbai.

Three species

In December 2018, a similar survey recorded the presence of three gorgonian species: Pseudopterogorgia fredericki, a species common along Mumbai's rocky shores; Menella indica, first described from Back Bay in 1870; and Echinogorgia sp, a more elusive inhabitant. These species were previously abundant in specific microhabitats; for instance, Echinogorgia dominated the exposed rocky surfaces, while Menella indica and P fredericki preferred the wave-flanked edges. "Menella indica holds historical significance. Its earliest recorded presence from the Indian coastline dates back nearly 150 years. That we can no longer spot it in its type locality is deeply concerning," said Dr Ghosh.

The spot off Chowpatty where the proposed Chhatrapati Shivaji Maharaj Memorial is slated to be built

Since its first description, the true identity and extent of Menella indica's distribution remains unknown as the species is not reported outside the type locality (place where a specimen is found). Patade, who has been documenting regional marine life through the citizen science platform iNaturalist, also confirmed the absence of these species in recent observations. "I was deeply disappointed and shocked to see the marine life nearly vanish, especially the gorgonians, which once thrived here in healthy, large colonies," said Patade.

Given that gorgonians are slow-growing and sessile, their abrupt disappearance is unlikely to be a result of seasonal variation. The researchers suspect a human-driven and natural causes, including coastal development, ongoing reclamation projects, sedimentation, and climate change, could be the primary reason behind the decline.

The proximity of the site to the proposed Shivaji Memorial raises concerns about the potential ecological impact of large-scale infrastructure development in sensitive marine zones. However, the team does not entirely rule out the possibility that these species may have migrated to deeper, less disturbed waters: a hypothesis that calls for more extensive underwater exploration and monitoring.

Unexpected coloniser

One of the most striking discoveries during the latest survey was the noticeable colonisation of Carijoa sp, commonly known as snowflake coral. Though its invasive status remains debated, its aggressive spread and ability to outcompete native species are well-documented. "We're seeing early signs of Carijoa engaging in space and resource competition. Without consistent monitoring, this could further disrupt the faunal composition of what little remains in this fragile habitat," said Patade.

Experts also pointed out that as Mumbai's coastline continues to undergo rapid transformation, the findings serve as a reminder of the delicate balance between development and conservation. They also feel that there is an urgent need for sustained marine biodiversity assessments, protective policy frameworks, and deeper public engagement in safeguarding the city's underwater heritage.