The Intertidal zone: Sandy beaches

Geetha Iyer

The ocean has neither received adequate attention nor any protection like the terrestrial biomes. It is only recently that it has been in the news. There is a lot about oceans that we need to be aware of if we have to care for it. Starting with this article I hope to bring to your attention some important aspects of the biodiversity of marine ecosystems and the varieties of habitats that encompass this large biome. Ocean ecosystems are varied and governed by a variety of complex factors. I will be touching upon only those that can be easily observed, studied and understood to serve as a foundation for moving to understand more complex issues.

Ocean brings to mind the seas and the seashore. The shores of the seas are where the land meets the water of the ocean. The boundaries are not fixed; where the land meets, the water changes with the cycle of low and high tides. This region, commonly known to us as the seashore or foreshore (the Foreshore Estate in Chennai comes to mind) is called the intertidal zone. An incredible variety of organisms live in this zone. This is the best place to start becoming familiar with marine biodiversity.

The defining feature of an intertidal zone is the periodicity of being exposed to air and remaining submerged under water. This is the result of the cyclic phenomenon of low and high tides. During low tides, the region is exposed to air and during high tides, completely submerged in water. The intertidal zone, depending on the geographical feature of that region, is often a mix of different habitats. Broadly speaking, at least three different types of habitats are evident – rocky shores, sandy beaches, or marshy mudflats – about which we have already discussed in a previous article on mangroves. There are other habitats of this zone too, but this article is restricted to sandy beaches.

Whatever be the type of habitat, the organisms living in an intertidal zone are specialized to deal with harsh and diametrically opposite conditions or abiotic factors.

Sandy beaches
Sandy beaches are among the most widely found intertidal zones and one which everyone can relate to easily. But these seemingly similar habitats are quite diverse. The beaches in Kanyakumari, Gulf of Mannar or Chennai have light coloured sandy beaches whereas those in the coast of Gujarat have dark sands. Beaches of southern India are rich in monazite, which is a thorium containing mineral. One of the most sought after tourist memento from Kanyakumari is the colourful sand packed in small packets. Little do people know that what they are carrying with them are radioactive materials that can expose them to small doses of radiation. The colourful sands have been found to have small concentrations of ²³²Th, ²³⁸U, and ⁴⁰K. That Koodankulam nuclear reactor built along this shore line is a testimony of the nature of the sand. These sands are a source of raw materials for the reactors.

Sandy beaches have other compositions too. Along the Konkan coast, coarse sand dominates the beaches whereas in places like Diu, the sand is high in silt content. Lakshadweep beaches have final coral sand.

Biodiversity of sandy beaches
Large vertebrate fauna in the beaches are limited to birds, turtles, fishes and some feral dogs. It is the invertebrate fauna that is fascinating to observe. Generally, sandy beaches have animals that are adapted for burrowing. Gastropod and Bivalve molluscs apart, many species of Cnidaria, Arthropoda and microorganisms can be observed. As the name suggests sand crabs and ghost crabs can be found in beaches that have coarse sands and are also inhabited by deep burrowing animals. Those with fine silt are preferred by gastropods such as the pretty Olive shells. Shores that are a fine mixture of coarse sand and silt sustain several detritus feeders. Crabs and burrowing bivalves are found in habitats that have non-coralline sand according to Dr Deepak Apte, former director of Bombay Natural History Society (BNHS). Then there are sponges, worms and marine plants that along with other creatures will surprise you with their wide ranging appearances and behaviours.

Activity 1: Intertidal walk to observe wildlife
The first mistaken notion that this walk will remove, is about the term wildlife. Wildlife for most are those animals that are seen in forests. What about the organism inside a shell that peeks out of the shell to see if it is safe to forage for food? Or the one that suddenly comes out of the sandy bottom during low tide? How about that mollusc that can actually give you a poisonous sting if you are not careful? The sting of a jelly fish, the dollar that suddenly appears or the scampering crab? They are all wildlife. Each unique in their own ways of appearance and lifestyle. An intertidal walk is the best way to become acquainted with the wildlife of the ocean.

Planning the walk
It is always good to survey the beach before taking a group of enthusiastic students for an intertidal walk. You have to first get rid of the thought that it is a walk to splash about in the sea.

Like a walk in the forest has set rules to follow, so too here. And it is as important to be disciplined because there are as many chances of accidents, bites and stings as in a forest.

I give below some important points for planning and execution of an intertidal walk; for some more details on precautions to be taken, read (definitely read) the ¹shorewalk-guidelines.

1. Find the tide timings and plan your walk when the tide is low.
2. Keep the number of students in the ratio 8-10 for every adult.
3. Distribute a set of dos and don’ts to students in advance and get a signed statement from parents for the walk. Students must especially be told that wading into the sea is not allowed.
4. Ensure that you have charted out the limits for exploration and let students know the boundaries for the walk.
5. Safety in this region requires a different approach. Never pick up a creature you have not observed and learned about. Many of the creatures will remain hidden. So avoid poking around with bare hands (sometimes even gloved hands are not going to protect you) or moving stones. Shells that may appear empty may actually have living creatures in them. The cone shell mollusc can sting you with a chemical that is a neuro toxin. Jelly fish, worms and some fishes can also harm you if you are not careful. The pistol shrimps can be fascinating to watch.
6. Low tide is the time when these creatures come out to feed. They may also be engaged in other activities such as mating, spawning, etc. Disturbance of any kind will not do them any good. So avoid moving them even if you have not been able to get a good photograph. Instead look for relationships. The mutualism, prey-predator, communal living that one learns about for terrestrial ecosystems are all seen among these intertidal creatures. Hermit crabs living inside molluscan shells, certain species of sea slugs living on certain species of cnidarians, the beaches are a theatre for life’s most fascinating drama.
7. Sketching, more than photography, helps you learn more about these creatures. Keep notes of what you see, the activities, the climatic conditions, etc.
8. You can take ambient and water temperatures.
9. Just be patient, stay put in a place and observe and the marine life will reveal itself to ^2,3you.
10. Discuss geographical features, tides, etc.
11. Note the status of the habitat. What kinds of pollution if any are seen? What are the likely disturbances to wildlife seen? Is there any other factor that might reduce the size of the habitat?
12. A number of questions can be asked to make the observation meaningful and for a full-fledged discussion in class for a better understanding of marine life.
13. At the end of the discussions in class, ask your students to prepare a shore-guide or a poster depicting the wildlife at the sandy beach they had visited. Let it be a hand drawn poster and not one with photographs stuck on a chart paper. They can also prepare cards for each of the animals they have seen-drawing of the creature and the most important features of the same.

Activity 2: Turtle study
Come October and the turtles come to the sandy beaches for nesting. Turtle walks are organized by NGOs and others who work in the field of Turtle conservation. Night walks to see the turtles come ashore, dig their nests, lay the eggs and then return to the sea has a powerful effect on a human being. Observing what can happen to the eggs if left unprotected will be a learning experience. Collecting the eggs and depositing them in safe hatcheries is something students of secondary and senior secondary classes can participate in. Finally releasing the hatchlings in water in the months of February onwards, will remain a powerful memory, which hopefully will lead to a posse of informed future citizens. WWF-India can be contacted to arrange for such walks. Two other ^6,7organizations that can help you are given in the reference section.

Threats to the habitat
Like wetlands, sandy beaches are also places that are earmarked for development agenda. They are mostly reclaimed to create land that can then be used for construction purposes, roads, buildings, etc. Many of the coastal road projects severely affect these zones leading to destruction of biodiversity. The organisms living in these zones are hardly looked upon or treated as wildlife.

Individual actions, alert public responses and action by citizen groups have managed to protect some areas. Raising awareness of these zones thus is very important.

Pollution is another process that is harming this habitat. Irresponsible tourism is a source of pollution. The ocean has become a dumping place and it starts at the intertidal zone. ⁴Pagadia fishing is a form of fishing in intertidal waters practiced by people of the Kutch region. A thermal power plant in Mundra that releases hot water into the sea has severely affected not only the fish population but also the nesting sites of the two highly endangered turtles – Green sea turtle and Olive ridley, which nest in these beaches. Despite the Coastal Regulation Zone Notification 2011 with its subsequent amendments, the degradation of sandy beaches and pollution continues unabated.

Beach cleaning now is a frequently undertaken activity. But not using the beaches to ⁵dump waste is a habit that needs to be cultivated. As dumping wastes is not the only threat this habitat faces, protection can start only with the right kind of awareness through education. A future generation that has been sensitized to these habitats and their importance is the way forward.

Intertidal walks can help in educating the young about the need to protect this habitat. It can be understood only through personal experiences, becoming aware of the unique wildlife found here.

References
1. https://www.marinelifeofmumbai.in/shorewalk-guidelines/
2. https://india.mongabay.com/2019/01/they-show-sea-life-on-the-sea-shore/
3. https://india.mongabay.com/2019/05/creatures-from-mumbais-shore-and-their-housing-stories/
4. https://india.mongabay.com/2019/05/march-of-industrialisation-tramples-kutchs-coastal-ecology/
5. https://india.mongabay.com/2020/03/keralas-fishing-beaches-littered-with-large-amounts-of-fishing-debris/
6. Students Sea Turtle Conservation network: https://sstcn.org/
7. https://www.dakshin.org/home/biodiversity-and-resource-monitoring/

The author is a consultant for science and environment education. She can be reached at scopsowl@gmail.com.