Adaptation is an evolutionary process whereby an organism becomes increasingly well suited to living in a particular habitat. It is not a quick process! Natural selection over many generations results in helpful traits becoming more common in a population. This occurs because individuals with these traits are better adapted to the environment and therefore more likely to survive and breed. Adaptation is also a common term to describe these helpful or adaptive traits. In other words, an adaptation is a feature of an organism that enables it to live in a particular habitat.

1. NOAKHALI SCIENCE & TECHNOLOGY UNIVERSITY
DEPARTMENT OF FISHERIES AND MARINE SCIENCE
ASSIGNMENT ON:
Topics 01: Adaptation of Marine Organisms to Different Environment
Topics 02: Global Warming Effect on Marine Fauna And Coral Islands
Course Title: Marine and Estuarine Ecology
Course Code: FIMS 4211

2. ADAPTATION OF
MARINE ORGANISMS TO DIFFERENT ENVIRONMENT
Adaptation is an evolutionary process whereby an organism becomes increasingly well suited
to living in a particular habitat. It is not a quick process! Natural selection over many
generations results in helpful traits becoming more common in a population. This occurs
because individuals with these traits are better adapted to the environment and therefore more
likely to survive and breed. Adaptation is also a common term to describe these helpful or
adaptive traits. In other words, an adaptation is a feature of an organism that enables it to live
in a particular habitat.

3. DIFFERENT TYPES OF ADAPTATIONS
1. Structural adaptations
2. Physiological adaptations
3. Behavioural adaptations
4. Biology Adaptation.

4. 1. STRUCTURAL ADAPTATIONS
Structural (or morphological) adaptations are the physical features of the organism. These
include things you can see, like its shape or body covering, as well as its internal
organisation. Following are a few of the ways that marine organisms have adapted their
physical features to suit a particular habitat.
Seawater is much denser than air – as a result, there are vast numbers of microscopic
organisms suspended in it. Cockles, as well as many other bivalves, are filter feeders. They
have adapted specialised siphon structures to filter these organisms and any other particles
of food from the surrounding water.

5. 1. STRUCTURAL ADAPTATIONS
Estuaries have quite variable conditions – tides, waves and salinity fluctuations affect the animals
and plants that live there on a daily basis. Many animals, such as cockles, are adapted to live in these
conditions. They have strong shells that protect them from wave action, drying out and the prying
beaks of predators.
Coastal plants need special adaptations to survive. For example, many types of seaweed attach
firmly to rocks so they are not swept away by waves. Their leaf-like fronds are tough and leathery,
which helps protect them from being torn by the waves or dried out by the sun.
Dolphins are mammals, but they look very different to mammals that live on land, as they are
adapted to living in water. They have a streamlined shape and fins instead of legs. They also have
blowholes on the tops of their heads. They use these to breathe, rather than through their mouths and
noses.

6. 2. PHYSIOLOGICAL ADAPTATIONS
Physiological adaptations relate to how the organism’s metabolism works. These adaptations enable
the organism to regulate their bodily functions, such as breathing and temperature, and perform
special functions like excreting chemicals as a defence mechanism.
Some marine mammals, such as whales, migrate over large distances and may spend time in a
combination of arctic, tropical and temperate waters. To cope with these temperature changes, they
are endothermic or ‘warm blooded’. This means that they are able to maintain a constant body
temperature that is not dependent on the surrounding water.

7. 2. PHYSIOLOGICAL ADAPTATIONS
Slow-moving species have adaptations that help protect them from predators. For example, many
marine organisms can only move slowly or not all. This means they cannot easily get away from
mobile predators, and they have other adaptations to protect them from being eaten. These can
include chemical defences in their skin, for example, sea stars.

8. 3. BEHAVIOURAL ADAPTATIONS
Behavioural adaptations are learned or inherited behaviours that help organisms to survive, for
example, the sounds made by whales allow them to communicate, navigate and hunt prey. Crab
larvae use sounds to help them find suitable habitats so they can settle and metamorphose (change
into an adult form).
Bryozoan colonies are found in high numbers on the continental shelf in New Zealand. They look
like plants but are actually made up of hundreds of tiny individual animals that have banded together
in order to more successfully find food and survive predation

9.  Lose weight to float: how fat really helps.
Each marine species adapt to the various habitats to reach an equilibrium, trying to solve problems that may
compromise its survival. One of the problems to be faced in the water is sinking. To face it we try to increase
the frictional forces with the diminution of the dimensions or increasing the size of the body as in the whales.
Other strategies are body shapes that help to remain in suspension without sinking (like the jellyfish’s
parachute shape) or lighten the body with mechanisms like gas production.
 Dinoflagellates: description and characteristics.
Dinoflagellates, also known as pyrophytes, peridines or dinoficee, are mostly unicellular and flagellate
microscopic algae, which represent one of the most important marine and freshwater phytoplankton groups
with more than 2000 living species.The cell has a peculiar structure, the anfiesma consists of a periplasto, in
the region below this can be present as cellulose veil. There are two flagella, both provided with lateral hairs,
different from each other for structure and orientation. There are two main morphotypes: the Dinoconte and
the Desmoconte. In the Dinoconte the cell has two grooves, an equatorial (cingulum) and a longitudinal
(furrow). The latter divides the cell into two parts, called epicone (or epiteca) and hypocono (or mortgage).
The two flagella emerge in the ventral position at the intersection between the cingulum and the furrow.

10.  Living in the dark: Noctiluca Scintillans(description and characteristics).
Noctiluca scintillans is a variety of microscopic algae and is one of the most commonly occurring
bioluminescent organisms in the world. Noctiluca is a single-celled organism large about 200-2000 μm in
diameter, spherical and gelatinous. There are several vacuoles and a network of cytoplasmic strands. It has
only one transverse flagellum and a striated tentacle extending posteriorly, which aid in movement and in the
capture of food. In nature, it has been found in two different forms called "red" and "green" respectively. The
"red" form is heterotrophic.
 Living in the dark: PelagiaNoctiluca(description and characteristics).
The Pelagia Noctiluca is a jellyfish commonly known as the luminous jellyfish, belonging to the Pelagiidae
family, the name Noctiluca derives from the green iridescence, of which it is endowed.The Pelagidae have a
relatively simple form: a bell without a ring channel, from the margins of which the tentacles depart, in which
the gastrovascular cavity is separated into uniform pockets and with oral "arms" extending like tentacles more
thick.They are commonly in the Mediterranean Sea and from eastern Atlantic Ocean to the North Sea, during
autumn and spring approaching the coast.

11.  Eels: a versatile species (description and characteristics).
The eels are marine animals that settle in most of the Mediterranean and the Atlantic Ocean. They are bony
fish that can survive safely in both fresh and salt water. They are considered an endangered species, due to
their prized meat. In fact, their presence has greatly diminished over the course of fifty years. They are
cylindrical and elongated fish, similar to crawling reptiles. In addition, their ability to cover certain stretches of
land outside the water makes them traceable to amphibian-like animals. The eels have a smooth skin,
completely covered with mucus and in appearance without scales but actually present, even if very small.
 Species mimicry: a defence mechanism (find an example).
We speak of cryptic mimicry (or cryptoism) to indicate the assumption of forms, colors and behaviors that
make the individual similar to the surrounding environment or parts of it, of fanerical mimicry (or ostentation)
to indicate the imitation of another species, toxic or dangerous, with aposematic colors. This is called mimicry
in the strict sense. Batesian mimicry occurs when an animal species, harmless and helpless in the face of
predators, exploits its resemblance to an aposematic species that lives in the same territory, coming to imitate
their color and behavior. In this way, in the predators' mind, the Batesian species is associated with the
aposematic one and therefore increases its chances of survival.

12. GLOBAL WARMING
EFFECT
ON MARINE FAUNA AND CORAL
ISLANDS
Coral reefs are the dominant coastal habitat in the tropical Pacific, representing more than 25% of
reefs globally – nearly 66,000 km2 (Wilkinson, 2004; Wilkinson, 2008). Many Pacific Islands and
Territories (PICTs), including French Polynesia, Kiribati and Palau have at least double the reef
area than land area (SPC data). Corals are the fundamental reef ecosystem engineers because they
construct the framework that supports over 600 species of calcifying corals, 4,000 species of fish,
as well as a high diversity of invertebrates, macroalgae and marine megafauna totalling
approximately 830,000 species of multicellular animals and plants worldwide, or 32 percent of all
named marine species (Allen, 2008; Fisher et al., 2015; Wilkinson, 2008).

13. The term ‘coral reef’ applies to a diversity of structures that grow in a wide range of habitats from clean
oceanic waters to areas close to continents, where the influence of land runoff can be considerable. The
eventual shape and form of the reefs will depend on this ambient environment and the underlying base
structure. Reefs predominantlygrow over previous reefs, that were killed off during massive sea Ieve l falls
during ice ages. The stony corals and calcareous algae gradually build up the calcium carbonate framework
until the reef reaches the sea surface, where atmospheric exposure limits further upward growth.
Barrier reefs develop along the edge of continental shelves that are sufficiently remote from sediment input
from the land to encourage vigorous coral growth. Usually behind these reefs are relatively deep water ways,
referred to as lagoons. Good examples are the Great Barrier Reef and the barrier reefs of Belize and New
Caledonia. These barrier reefs protect the adjacent shorelines from the impact of oceanic waves.
Platform reefs grow over ‘hills and mountains’ formed by previous reefs or other features such as sand dunes,
formed when sea level was lower. Once the reefs reach the surface, they grow outward often forming large
areas of reef flats. Platform reefs are frequently found within the large lagoonsformed by barrier reefs. There
are good examples of platform reefs in the Bahamas, within the ‘lagoon’ of the Great Barrier Reef and in the
Red Sea.

14. The growth and functioning of coral reefs is best under the following general conditions
water temperatures in the optimum range of about 23-30°C;
consistent irradiance, hence shallow, clear seas in tropical latitudes;
low levels of sedimentation;
low concentrations of inorganic and organic nutrients;
• Macro and Micro-algae on Reefs : The other major primary productivity component of coral reefs are the
benthic macro- and micro- algae that coat many of the ‘bare’ surfaces (see Box 2.2). Calcareous or coralline
algae not only photosynthesize, but also produce substantial amounts of calcium carbonate. Their role on
many reefs is so important that it has been suggested that ‘coral’ reefs is a misnomer, and a more accurate
term would be ‘algal’ reefs (Hillis-Colinvaux 1986). The calcareous algae function in two ways: Halimeda
are foliose algae which make major contributions to the loose sediments of many reefs; encrusting algae
such as Lithothamnion make important structural contributions to the reef by binding and cementing reef
surfaces into a durable limestone plate or block. This algal cementation is most pronounced in high energy
environments, such as on the reef crest, shallow reef flats, and the seaward intertidal zone of reef islands.

15.  Plankton
Plankton are the microscopic plants and animals that inhabit the water and whose large and medium-scale
movements are controlled primarily by water motion. Plankton are important to coral reef ecosystems since
they serve as food and nutrients for animals higher in the food chain, and because many important coral reef
species have planktonic larvae which act as the long distance dispersal mechanism between reef areas (Box
2.6). These larvae are transient members of the plankton, but their survival is crucial to the reproduction and
recruitment processes of a coral reef. Plankton communities predominantly drift in the upper few metres of the
water column and hence are susceptible to changes in the amount of incident light, UV radiation, temperature
and water movement (Box 2.3).

16.  Planktonic Larvae
Corals exhibit two spawning strategies for sexual propagation, both producing planktonic larval stages. Most
numerous are the broadcast spawners, which release (sometimes simultaneously) millions of eggs and sperm
that develop into free swimming larvae. These drift in the upper layers of the plankton for 4 to 7 days before
seeking suitable reef substrata. In the other type of larval reproduction, some corals (brooders) hatch within
their tissue better developed propagules which have a very short (hours) free swimming stage (Harrison and
Wallace 1990). The vast majority of reef fish also have planktonic larvae. The duration of larval life varies
considerably from 3 weeks to well over 3 months (Leis 1991). Many other reef organisms spend time in the
plankton. One important group within this listing is the larvae of the crown-of-thorns starfish, Acanthaster
p/anci, a predator of corals with episodic population explosions. Variations in conditions affecting the 3week
larval life may explain these periodic outbreaks.