Exploring the Intertidal Zone: The Hidden World Between Tides

Exploring the Intertidal Zone: The Hidden World Between Tides 

As India's coastal ecosystems host a vast array of marine organisms, a large portion of this biodiversity remains uncatalogued and undervalued. To bridge this knowledge gap, the India Intertidal Bioblitz was launched as an innovative project, conducted from January 26, 2025, to February 4, 2025. The initiative took place across Mumbai, Goa, Visakhapatnam, and the Andaman Islands, bringing together researchers, conservationists, and keen volunteers to explore and document the rich marine life thriving in these intertidal zones. 

What is the Intertidal Bioblitz? 

The Intertidal Bioblitz is a survey where researchers and volunteers work together to identify and record as many species as possible within a short time in a specific area. The India Intertidal Bioblitz is a joint effort led by the Coastal Conservation Foundation (CCF) and the East Coast Conservation Team (ECCT). This initiative focuses on intertidal zones, the areas between the highest and lowest tides. These zones are home to many marine species that can survive both underwater and in exposed conditions. 

Participants of India's first Intertidal Bioblitz actively explore the tide pools along the Visakhapatnam coast, documenting diverse marine species in their natural habitat. (Image Courtesy: citsci-ind.org) 

What is the Intertidal Zone and Why is the Bioblitz Conducted? 

The intertidal zone is the coastal area between the high and low tide marks. This unique habitat undergoes constant environmental changes, making it home to a diverse range of marine species that can survive both underwater and in exposed conditions. Intertidal zones play a crucial role in coastal ecosystems by serving as breeding grounds for marine life, acting as natural barriers against erosion, and storing carbon through seagrass beds and mangroves. 

To ensure conservation efforts are guided by scientific data, the Intertidal Bioblitz was conducted as a large-scale survey to document and monitor these fragile ecosystems. The initiative aimed to track biodiversity trends, assess the impact of climate change and human activities on intertidal marine life, and raise awareness about the ecological significance of these habitats. Researchers and citizen scientists collaborated in this effort, contributing to a deeper understanding of India’s coastal biodiversity. 

Key Discoveries and Findings 

The Intertidal Bioblitz recorded over 3,600 observations and identified 514 unique species across India’s coastal regions. This extensive data collection provided valuable insights into the country’s rich intertidal biodiversity. 

• New Records: A remarkable discovery was the documentation of Pseudoceros bifascia along the coast of Andhra Pradesh. Previously thought to be restricted to the Lakshadweep archipelago, this finding marks the species’ first recorded presence on the Indian mainland. It highlights the importance of ongoing research and conservation efforts in uncovering new aspects of marine biodiversity. 

Regional Highlights 

Visakhapatnam 

Participants recorded 1,533 observations, identifying a total of 227 species. The survey led to the discovery of a few previously unclassified species and over ten species newly documented in the region. Nighttime exploration of the intertidal zone revealed a fascinating variety of marine life, including butterfly fish, porcupine fish, surgeonfish, moray eels, and juvenile angelfish. 

Mumbai 

In Mumbai’s intertidal zone, 120 species were recorded. Some notable finds included the old-woman octopus, orange-striped hermit crab, mangrove leaf slug, tiger moon snail, and the highfin moray eel. 

Andaman Islands 

Surveys conducted across three locations in the Andaman Islands documented over 70 species. Observers found a rich diversity of marine life, including bubble snails, flatworms, sea slugs, moray eels, octopuses, and juvenile stingrays. The region's coral-rich habitats contrast sharply with the sponge and hydroid-dominated coasts of Maharashtra and Goa, highlighting the unique biodiversity of India’s coastal ecosystems. 

A close-up of a ghost crab spotted during India's Intertidal Bioblitz, highlighting the rich and often overlooked biodiversity of India's coastal ecosystems. (Image Courtesy: inaturalist.org) 

The Role of Citizen Science 

The success of the Intertidal Bioblitz highlights the significant impact of citizen science in ecological conservation. By involving local organizations, researchers, and nature enthusiasts, the initiative fostered a deeper connection between people and their coastal environments. 

Participants, under expert guidance, developed skills in careful observation, accurate species identification, and detailed data recording. These documented findings were then shared on platforms like iNaturalist, enabling researchers worldwide to access and analyze the data. This collaborative effort not only expanded scientific knowledge but also strengthened public awareness and engagement in coastal conservation. 

Conservation Implications 

The extensive data collected through the Intertidal Bioblitz provides a critical foundation for monitoring changes in coastal ecosystems, which face numerous threats, including: 

Habitat Degradation 

Rising tourism and coastal development are leading to habitat destruction, often worsened by pollution. A notable example is the degradation of marine habitats near Andaman’s Natural Bridge, where increased tourism has contributed to the decline of certain marine species due to overconsumption and habitat loss. 

Climate Change 

Rising sea temperatures and ocean acidification are major threats to marine life, triggering events like coral bleaching. The widespread bleaching event of 2024 severely impacted all soft corals in the Andaman region, prompting ongoing efforts to assess the damage and accelerate ecosystem recovery. 

Shifts in Species Distribution 

The data also highlights significant changes in species composition. For instance, carpet sea anemones are gradually displacing pearly sea anemones in some tide pools, indicating potential ecological shifts that require further study. 

These findings emphasize the urgent need for conservation initiatives to protect intertidal ecosystems from human activities and climate change. 

A healthy seagrass bed discovered in the intertidal zone, providing a critical habitat for marine life and acting as a natural carbon sink. (Image Courtesy: sustain.round.glass) 

Future Directions 

Building on the success of the Intertidal Bioblitz, future efforts aim to expand research, strengthen conservation policies, and deepen community engagement: 

• Expanded Surveys: Extending studies to additional coastal regions will provide a more comprehensive understanding of India’s intertidal biodiversity. 

• Policy Advocacy: Using collected data to influence conservation strategies and ensure the long-term protection of critical marine ecosystems. 

• Community Engagement: Promoting awareness through educational workshops, field expeditions, and academic programs to foster a culture of conservation and responsible environmental stewardship. 

The India Intertidal Bioblitz has highlighted the incredible diversity of marine life along the country’s shores. By combining community participation with scientific precision, this initiative has laid the foundation for continued research and conservation efforts. Moving forward, the collaboration of scientists, policymakers, and local communities will be essential to safeguarding these fragile ecosystems for future generations.