Biological and chemical oceanography.Chemical Oceanography is fundamentally interdisciplinary. The chemistry of the ocean is closely tied to ocean circulation, climate, the plants and animals that live in the ocean, and the exchange of material with the atmosphere, cryosphere, continents, and mantle

1. Dr. M. Belal Hossain
M.S. (CU), M.Sc. ( UK), PhD (Brunei)
Associate Professor
FIMS, NSTU
Biological and Chemical
Oceanography

2. Course rationale:
• To know the classification, distribution of phytoplankton, zooplankton,
nekton, and benthos.
• To know the relationship between phytoplankton and zooplankton and also
between the plankton and fish.
• To know the interactions among the marine biota.
• To know the productivity of oceans.
• To know the chemistry of sea water.

3. Syllabus
1. The sea/ocean as a biological environment Ecological Groups and some of
their adjustments: Classification of the Marine environment, General Character
of population of the primary biotic divisions
2. Benthos : Defn, types, major groups, factors affecting distribution,
3. Zooplankton: Defn, types, major groups, food and feeding habits, factors
affecting growth and distribution, seasonal distribution, vertical distribution
and migration of Zooplankton
Chemical Oceanography:
Chemistry of sea water
1. Composition of sea water (elements present in the sea water), constancy of
composition,
2. Dissolved gases in sea water, Distribution of O2 and CO2 in sea water
3. Distribution of Nitrogen compounds (Nitrite, Nitrate)
4. Distribution of Phosphate, Distribution of Silicate

4. 1. Overview:
2. The sea/ocean as a biological environment:
2.1. Classification of the Marine environment
2.2. General Character of population of the primary biotic
divisions
3. Summary
4. Recommended books

6. 2.1. Classification of the Marine environment:
Marine environment is divided into two major realms, the benthic and
the pelagic, based upon the ecological characteristics and marine life
associated with them.
The Benthic Realm: The benthic realm refers to the floor of the oceans,
extending from the high tide line to the greatest ocean depths. The
organisms that live in or on the bottoms are called benthos. The benthic
realm is subdivided on the basis of depth into the littoral zone, which
extends from high tide to a depth of about 200 m (660 ft), and the deep-sea
realm.
Benthonic plants can live only in the euphotic zone, the uppermost 100–200
m (330–660 ft) of the ocean, where sunlight penetrates. Benthonic animals
that live below the euphotic zone often must depend on the rain of organic
debris from above to supply their food needs

7. The Pelagic Realm: The pelagic realm consists of all of the ocean water
covering the benthic realm. It is divided horizontally into the neritic or
fertile near-shore, province and the oceanic province. Vertically it is
divided into the euphotic, or photic, zone and the aphotic (without
sunlight) zone.
Drifting, free-floating organisms, called plankton, and organisms with
poor mobile ability populate the euphotic zone. Most plankton are
microscopic or near-microscopic in size. Phytoplankton are photosynthetic
bacteria (cyanobacteria) and floating algae, such as diatoms,
dinoflagellates, and coccolithophores. Heterotrophic plankton
(zooplankton) are floating animals and protozoan’s of the sea and rely on
the phytoplankton as food sources. Foraminifera and radiolaria are the
dominant protozoan zooplankton that secretes tests (shells), which
become incorporated into the sediment of the ocean floor.

8. 2.1. Classification of marine environment:
i. Pelagic region: It includes the entire water mass of the ocean. It is further
subdivided into two regions, namely- neritic zone and oceanic zone.
Neritic zone: The shallow water region of the shore is called neritic zone. It
lies in the continental shelf which is the gradual slope from the shore into
the sea. It extends to a width of 16 to 240 km and to a depth of 200 metres.
As this zone is connected with the land, factors of terrestrial environment
influence it much.
Oceanic region: It refers to the open sea beyond the continental shelf. The
entire water body remaining beyond the depth of 200 meters constitutes
the oceanic zone.
ii. Benthic region: It consists of the floor of the sea. It is subdivided into two
regions, namely- littoral zone, and deep sea.
Littoral zone: The littoral zone or intertidal zone is that shore area lying
between the extremes of high and low tide; it represents the transitional
area from marine to terrestrial conditions. It is a zone of abundant of life.
Littoral zone is further sub-divided into two regions, namely eulittoral zone
and sublittoral zone.
The eulittoral zone extends from the high tide level to a depth of about 40
to 60 meters.
The sublittoral zone extends from this level to a depth of about 200 meters
or the edge of the continental shelf.

9. Deep sea: The deep sea is divided into three regions, namely bathyal,
abyssal, and hadal.
The bathyal zone is that area of bottom encompassing the continental slope
and down to about 4000 meters.
The abyssal zone includes the broad abyssal plains of the ocean basins
between 4000 to 6000 meters.
The hadal is the benthic zone of the trenches between 6000 to 10000 meters.
Based on penetration of light, the oceanic zone is divided into two strata.
They are the upper euphotic or photic zone and the lower aphotic zone.
i. Photic zone: The photic zone is the lighted zone, and it extends to a depth
of 200 meters. A synonym for this zone is the epipelagic zone.
ii. Aphotic zone: The permanently dark water mass below the photic zone is
the aphotic zone. The pelagic part of the aphotic zone can be divided into
zones that succeed each other vertically.
The mesopelagic is the upper most of the aphotic areas. Its lower boundary in
the tropics is the 100C isotherm, which ranges from 700 to 1000m, depending
on the area.
The bathypelagic zone is lying between 10 and 40C, or in depth between 700
and 1000 m and between 2000 and 4000 meters.
Overlying the plains of the major ocean basins is the abyssalpelagic, which
has its lower boundary at about 6000 meters.
The open water of the deep oceanic trenches between 6000 and 10000 m is

10. 2.2.General character of population of the primary biotic divisions
1.Benthos: Benthos are included the sessile, creeping, and burrowing
organisms found on the bottom of the sea. Representatives of the group
extend from the high-tide level down into the abyssal depths. The benthos
comprises-
Sessile animals, such as the sponges, barnacles, mussels, oysters, crinoids,
corals, hydroids, bryozoa, some of the worms, all of the seaweeds and eel
grasses, and many of the diatoms.
Creeping forms, such as crabs, lobsters, certain copepods, amphipods, and
many other crustacean, many protozoa, snails, and some bivalves and fishes.
Burrowing forms, including most of the clams and worms, some crustacean,
and echinoderms.
2.Nekton: The nekton is composed of swimming animals found in the pelagic
division. In this group are included most of the adult squids, fishes, and
whales- namely, all of the marine animals that are able to migrate freely over
considerable distances. Obviously, there are no plants in this general group.
3. Plankton: The plankton is included all of the floating or drifting life of the
pelagic division of the sea. The organisms, both plant and animal, of this
division are usually microscopic or relatively small; they float more or less
passively with the currents and are therefore at the mercy of prevailing water
movements.

11. Three major groups in the Ocean:

13. Benthic Environment

14. Ecological Groups and some of their adjustments:
1. Benthos : Defn, types, major groups, factors affecting distribution
Benthos : Live in or on the sediment and thus in
close contact with the substrata in aquatic habitat (Levinton, 2001; Elliot,
1993).
Classification of benthos: On the basis of habitat types benthos are
three types- 1. Epifauna, 2. Infauna, 3. Semi infauna
Epifauna: Organisms live attached to a hard surface or rooted to the
shallow depth below the surface. E.g. Oyster
Infauna: Organism live below the sediment water interface. E.g. Clams,
polychaetes.
Semi infauna: Organism live partially below the sediment water
interface, but protrude above. E.g. Sea pens, some mussel
On the basis of size benthos are three types
1. Macrobenthos : Organisms whose shortest dimension is greater than
or equal to 0.5 mm.
2. Meiobenthos: Organisms are smaller than 0.5mm. but larger than
micro benthos.
3. Microbanthos: Organisms are less than 0.1 mm in size.

16. On the basis of feeding benthos are
1. Suspension feeders
2. Deposit feeders
3. Harbivores
4. Carnivores
Suspension feeders: They feed by capturing particle from
the water. E.g. Sponges
Deposit feeders: They ingest sediment and use organic
matter and microbial organisms in sediment as food. E.g.
Gastropodes, polychaetes.
Harbivores: They eat non microscopic plants, such as sea
weeds and sea grasses. E.g. Urchins, Some polychaetes.
Carnivores: They eat other animals. E.g. Crabs, Starfish.

17. Benthos are further classified as follows: (include main charecteristics from
Text book).
kingdom Protozoa: characteristics:
1. grade of construction: Single autonomous cell.
2. Symmerty: variable.
3. Nervous system: none.
number of the species: Over 30000
Example: Ciliate, foraminifera.
Phylum Porifera: Characteristics:
1. Grade of construction: Cellular.
2. Symmerty: variable.
3. Segmentation: none.
Number of the species: 5000
Example: Sponges
Phylum Cnidaria:
Characteristics:
1. Grade of construction: Two tissue layer.
2. Symmerty: Radial.
3. Other features: two basic stages- sessile polyp and swimming medusa.
Number of the species: 9000
Example: Hydrozoa (Tubulariua), Scypgezoa(true jellyfiah), Anthozoa(corals,
anemones).

18. Phylum Platyhelminthes: Characteristics:
1. Grade of construction: organ derived from three tissue layers.
2. Type of gut: Blind.
3. Segmentation: none.
Number of the species: 12,000. They are found in crevices, under rocks, and
sometimes on bare sediment surfaces.
Example: different species of flatworms e.g., Schistosoma mansoni.
Phylum Nemertea: Characteristics:
1. Grade of construction: organ derived from three tissue layers.
2. Symmerty: Bilateral.
3. Segmentation: none.
Number of the species: Greater than 800. They have a proboscis and a
complete gut and are mobile carnivores that burrow through the sand.
Example: Different species of ribbon worm.
Phylum Nematoda: Characteristics:
1. Grade of construction: organ derived from three tissue layers.
2. Symmerty: Bilateral.
3. Segmentation: none.
Number of the species: 12,000. Roundworms are among the most
widespread of all marine invertebrates and often have population densities
of millions per square meter of mud.
Example: Round worm

19. Phylum Annelida
Characteristics: 1. Type of gut: complete with anus
2. Symmerty: Bilateral
3. Segmentation: present
Number of the species:12000 (Earthworm, sandworm, lugworm)
Example: Segmented worm
Phylum Sipuncula-(Peanut worm)
Number of the species:About 300
Phylum Ponogonophora-(Gutless wonders)
Number of the species:100
Phylum Mollusca-(Shelled organisms) : Characteristics
1. Type of gut: complete with anus
2. Symmerty: Bilateral
3. Segmentation: Absent
Number of the species:100000 (Clams, squids, snails, octopus)
Examples: Tegula (snail)
Phylum Arthropoda-(Jointed appendages) : Characteristics:
1. Have jointed appendages
2. Symmerty: Bilateral
3. Circulatory system : Open
Number of species: over one million (Shrimp, crab, sow bugs, insects)
Examples: Macrobrachium

20. Phylum Echinodermata-(Five-fold symmetry)
Characteristics
1. Type of gut: Blind sac with very reduced anus
2. Symmerty: Radial
3. Segmentation: Absent
Number of species: Approximately 6000 (Starfish, sea urchin,Sea
cucumber)
Example: Star fish (Asteroidea)
Phylum Urochordata-(Sea Squirts)
Number of species:1200
Others:
1. Phylum Bryozoa-(Moss)
Number of species:4000
2. Phylum Branchiopoda-(Lingulas)
Number of species:300
3. Phylum Phoronida-(Worm like
Number of species: Approximately 10

21. Distribution of Benthos
A. Global distribution: in different oceans (include more info from text
book)
B. Local distribution: regional distribution in different countries, ex.
estuary
Factors affecting the distribution:
1. Salinity
2. Dissolved O2
3. Organic matter
4. Sediment grain size
5. Food availability
6. Seasons
7. Habitat types
8. Biological attributes
9. Anthropogenic influences
10. Climate change

22. Local distribution:
Distribution of benthos in the Meghna Estuary:

26. Dendogram of fauna abundance data of Meghna
river estuary

27. Ordination for the species abundance data

32. Salinity:
Salinity put a physiological limitation upon organisms, and organisms which can
osmoregulate across a broad salinity range (euryhaline) are distributed
throughout the estuary, whilst stenohaline are limited to a narrower salinity
range and thus confined themselves in a definite zone.
Remane (1934) postulated that species richness was greatest in marine waters,
moderate in freshwater, and least in waters with salinities between 5 and 8.
Attrill (2002) examined the relationship between species richness and variation
in salinity, rather than with average salinity. He found that the diversity of
assemblage was highest in the more stable marine waters than in areas where
salinity was most variable and then increased in consistently freshwater.

33. Dissolved Oxygen :
- Diversity/ density Increase with increasing DO
Organic matter:
- Certain benthos increase with increasing OM
- But mostly decrease with increasing OM as low DO
- under conditions of significant organic enrichment, extensive
microbial breakdown of the organic matter can result in low oxygen
or hypoxic environments, which may reduce the diversity of
macroinvertebrates.

34. Food Availability:
Although grain size was found to regulate the distribution of benthic
invertebrates, it has been suggested that restrictions on grain size may
often be a link of food availability, with smaller grain sizes generally having
a higher organic content whilst also being more suitable for larvae with
small mouth parts.
Habitat types: Nature of habitat or structural complexity of the estuarine
bed can also play important role in controlling the distribution
macroinvertebrates as estuarine habitats are extremely heterogeneous,
comprising a variety of substrata from non-vegetated soft mud, fine and
coarse sand to vegetated saltmarsh, algal mats, seagrass beds, and
mangrove swamps. These heterogeneous habitats are predicted to
increase biodiversity through an increase in habitat stability (e.g.,
protection from wave action); greater protection from predation; the
creation of niches (habitat and resources) and inter-specific mutual
relationships; and a reduction in the competitive displacement by robust,
generalist (broad niche) species due to an increase in resources (e.g. food
and habitat) (Wall, 2004). For example, seagrass beds have been shown to
support significantly more productive and species-rich macroinvertebrate
communities than similar unvegetated substrates.

35. Grain size/ texture
sediment is more than just a habitat as many infaunal species utilize it for locomotion;
protection from predators and the environment; as a structure for burrowing or case
building; and as a source of food, as in the case of deposit feeding organisms. Coarse
sediments were identified as containing more diverse assemblages, while finer
sediment was typically dominated by a few common species.
-as a 'super parameter,' a variable, strongly correlated with the other variables, e.g.,
dissolved oxygen, salinity, organic matter, and porosity, which may be important in
controlling the distribution of benthos.
-grain size was a crucial factor in the distribution of macroinvertebrates among
different feeding guilds, with the underpinning conjecture that suspension-feeders are
predominantly found in sandy environments and deposit feeders in softer, silty-clay
sediments
-grain size may sometimes inhibit the ability of some taxa to inhabit an environment,
e.g., restrict the consumption of sedimentary particles due to the clogging of gills in
turbid sediment-water interfaces
-sulfide accumulation in reduced sediments sometimes acts as lethal factors for
benthic macroinvertebrates in eutrophicated brackish water

36. Seasons :
Macroinvertebrate communities also respond to seasonality effects,
especially in the Indo-Pacific tropical estuaries. Organisms exhibit peak
abundance in autumn, whereas minimum abundance in wet monsoon
season. During wet months, macrofauna suffer from increased mortality as
high fresh water flow reduces the salinity. Densities are typically lower in
cooler months than warmer periods as a result of the effects of
temperature on both metabolic and reproductive success.

37. Biological attributes:
redation, competition, larval recruitment) have also been shown to
influence the macrofaunal abundance. Ecosystem engineers (e.g.,
rag worms) in some intertidal zones can alter the whole macrofaunal
community structure by bio-turbation, habitat creation, modification,
and facilitation processes.
Anthropogenic influence:
In most estuaries of the world, the stress of natural variables is
intensified further by various human interventions (land reclamation;
dredging; shipping; harbor facilities; power generation by making
barrages; establishing industrial and urbanized centers; and waste
drainage from domestic, industrial and agricultural activities. For
instance, sewage released into estuarine environment often leads to
eutrophication, which results into a shortage of oxygen and
occurrence of hydrogen sulphide in the sediment, resulting in related
reduction in the diversity of fauna. Dredging can have possible
calamitous effects by erosion and remobilization of pollutants from
sediments with accompanying gain in turbidity removal of organisms
with the sediment

38. Recommended books:
1. Nabakken, J.W. 1997. Marine Biology- An Ecological Approach. Addison
Wesley Longman, Inc. California.
2. Pandey, Kamaleshwar and J.P. Shukla. 2007. Fish and Fisheries. Rastogi
Publications. Meerut- India.
3. Levinton, Jeffrey. S. 1995. Marine Biology- Function, Biodiversity,
Ecology. Oxford University Press. New York.
4. Morrissey, John. F., and James. L. Sumich. 2009. Introduction to the biology
of marine life. Jones and Bartlett Publishers. Boston.
5. Anikouchine, William. A., and Richard. W. Sternberg. 1973. The World
Ocean- an introduction to oceanography. Prentice-Hall, Inc.,
6. Gross, M. Grant. Oceanography- a view of the earth. 1972. Prentice-Hall,
Inc, New Jersey.
7. Sverdrup, H.U., Martin. W. Johnson and Richard H. Fleming. 1970. The
Oceans- their physics, chemistry, and general biology. Prentice-Hall, Inc,
New Jersey.
8. Ross, David. A. 1970. Introduction to oceanography. Appleton-Century
Crofts (Meredith Corporation). New York.
9. Welch, Paul. S. 1951. Limnology. McGraw-Hill Book Company. New York.
10. Thurman, Harold. V. 1994. Introductory Oceanography. Macmillan
Publishing Company. New York.
11. Tait, R.V. 1972. Elements of Marine Ecology. Butterworth’s, London.

39. Thank you