This document provides an overview of marine ecology. It begins by discussing ocean currents, including the factors that drive them and their influence on climate. It then describes the major types of marine organisms - nektonic, planktonic, and benthic. Microbes like bacteria, archaea, and protists are introduced. Primary producers like phytoplankton, seaweeds, and their characteristics are outlined. Finally, the document examines some invertebrate phyla found in marine ecosystems like sponges, cnidarians, mollusks, arthropods, and echinoderms.

1. Bio 421
Marine
Ecology
Ms. Faith Sereño
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2. Learning Objectives
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 Ocean Currents
 Marine Organisms
 Marine Microbes
 Multicellular Primary Producers
 The Marine Invertebrates

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Ocean Currents
Ocean currents are patterns of water movement that influence climate
zones and weather patterns around the world. They’re primarily driven by
winds and by seawater density, although many other factors – including
the shape and configuration of the ocean basin they flow through –
influence them.

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What are the factors affecting ocean currents?
Winds, water density, and tides all drive
ocean currents. Coastal and sea floor
features influence their location, direction,
and speed.
Earth’s rotation results in the Coriolis effect
which also influences ocean currents.

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Surface Currents
Large-scale surface ocean currents are driven by
global wind systems that are fueled by energy from
the sun.
These currents transfer heat from the tropics to the
polar regions, influencing local and global climate.

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Deep Ocean Currents
Differences in water density, resulting from the variability of water
temperature (thermo) and salinity (haline), also cause ocean currents.
This process is known as thermohaline circulation. In cold regions, such
as the North Atlantic Ocean, ocean water loses heat to the atmosphere
and becomes cold and dense.
When ocean water freezes, forming sea ice, salt is left behind causing
surrounding seawater to become saltier and denser. Dense-cold-salty
water sinks to the ocean bottom. Surface water flows in to replace the
sinking water, which in turn becomes cold and salty enough to sink.
This "starts" the global conveyer belt, a connected system of deep and
surface currents that circulate around the globe on a 1000 year time
span. This global set of ocean currents is a critical part of Earth’s
climate system as well as the ocean nutrient and carbon dioxide cycles.

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Biological Influence
Ocean currents are an important abiotic factor that
significantly influences food webs and
reproduction of marine organisms and the marine
ecosystems that they inhabit.
Many species with limited mobility are dependent
on this "liquid wind" to bring food and nutrients to
them and to distribute larvae and reproductive
cells.

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Marine Organisms
Marine organisms may be classified (according to their mode of
life) as nektonic, planktonic, or benthic.
Nektonic animals are those that swim and migrate freely, e.g.,
adult fishes, whales, and squid.
Planktonic organisms, usually very small or microscopic, have
little or no power of locomotion and merely drift or float in the
water.
Benthic organisms live on the sea bottom and include sessile
forms (e.g., sponges, oysters, and corals), creeping organisms
(e.g., crabs and snails), and burrowing animals (e.g., many clams
and worms). Seafloor areas called hydrothermal vents, with giant
tube worms and many other unusual life forms, have been
intensively studied by marine biologists in recent years.

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Distribution of Marine Organisms
The distribution of marine organisms depends on the chemical and
physical properties of seawater (temperature, salinity, and dissolved
nutrients), on ocean currents (which carry oxygen to subsurface
waters and disperse nutrients, wastes, spores, eggs, larvae, and
plankton), and on penetration of light.

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Photosynthetic organisms (plants, algae, and cyanobacteria), the primary sources
of food, exist only in the photic, or euphotic zone (to a depth of about 300 ft/90 m),
where light is sufficient for photosynthesis.
Since only about 2% of the ocean floor lies in the photic zone, photosynthetic
organisms in the benthos are far less abundant than photosynthetic plankton
(phytoplankton), which is distributed near the surface oceanwide.
Very abundant phytoplankton include the diatoms and dinoflagellates (see
Dinoflagellata). Heterotrophic plankton (zooplankton) include such protozoans as
the foraminiferans; they are found at all depths but are more numerous near the
surface. Bacteria are abundant in upper waters and in bottom deposits.

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Biological Concepts
All living organisms are composed of cells, which are the basic units of life.
Cells contain all the chemical compounds necessary to support life and to
pass on their genetic information.
Building blocks of life: macromolecules
Carbohydrates – used for energy & structure within cells
Lipids – store energy / insulation to trap heat in cold climates
Proteins – complex structure of protein to perform important functions
Nucleic acids - contains all the genetic material

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Evolution and natural selection
In 1831 Charles Darwin sailed aboard the HMS Beagle for a 5 year
voyage around the world.
He was already familiar with the process of artificial selection,
selection being forced by human hands, for instance through
practiced farmers breeding animals for a
certain desired trait.
Darwin suggested that a similar process may be happening in the
wild through natural selection.

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Formation of New Species
Speciation refers to the formation of new species from previously
existing ones. A common way in which new species arise is through
habitat isolation, when two or more populations of the species
become geographically isolated, perhaps through migration or
geological change.

14. Marine Microbes
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Micro-organisms are the most abundant organisms in
the oceans.
They include viruses, prokaryotes, protists and
some fungi. Even though they are not visible to the
naked eye they have very important ecological roles.
They are the basis of the food chains and play an
important role in decomposition and recycling of
nutrients.

15. Marine Virus
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Marine viruses are extremely abundant in the oceans and
play an important ecological role.
Marine viruses are 10 times more abundant than marine
prokaryotes.
Viruses are generally not considered to be alive because
they have no metabolism, and can only reproduce by
injecting their DNA into a host, which is called
viral replication.

16. Marine Bacteria
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Most marine bacteria are rod-shaped (bacillus) or spherical (coccus) and are small,
between 200 nanometers to 750 micrometers in length.
Cyanobacteria are also known blue-green algae. They are the only
photosynthetic prokaryotes and in fact photosynthesis has evolved only
once, in this group.
Many species of cyanobacteria can use N2 as a source of nitrogen—
allowing them to thrive where low levels of nitrogen nutrients.

17. Marine Fungi
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Fungi are eukaryotes with cell walls made of chitin
They are heterotrophs and use exoenzymes to digest organic
matter. A large proportion of fungi are decomposers important in
recycling organic matter. Fungi are strict aerobes; anaerobic
decomposition is carried out by bacteria.
Marine fungi are not very abundant (less than 1% of fungi are
marine), and they are mostly microscopic

18. Marine Protists
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Diatoms are important members of both planktonic and
benthic communities.
Dinoflagellates are globular, single-celled organisms which have
two flagella that lie in grooves on the cell’s surface. One of the
flagella creates forward propulsion while the other makes the
dinoflagellate spin.
Dinoflagellates are one of the most important groups
responsible for harmful algal blooms, also known as red
tides.
They are photosynthetic primary producers and they are large
phytoplankton and require large amounts of nutrients.

19. Multicellular Primary
Producers
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Most of the primary production in the oceans is carried
out by phytoplankton (diverse species of photosynthetic
micro-organism that live in the water column), which are
small yet extremely abundant.
Multicellular primary producers (seaweeds and flowering
plants) need to be attached to the benthos and for that
reason are limited to shallow coastal areas.

20. Seaweeds
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There are three groups of multicellular macroalgae (seaweeds): the
red algae, the green algae, and the brown algae.
Green Algae: Phylum Chlorophyta
Green algae have the same pigments as vascular plants:
chlorophyll a, b, and carotenoids.
Most species of green algae are found in freshwater and
most of those in the marine environment are microscopic.

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Red Algae: Phylum Rhodophyta
The red algae are primarily marine and are most diverse in the tropics.
Red algae are harvested commercially for many uses. They are harvested
for agar and carrageenan which are used for their gel-forming capacity in
pharmaceuticals and foods
(e.g. laboratory gels, ice creams, cosmetics, salad dressings).
Brown Algae: Phylum Phaeophyta
The species in this phylum are almost exclusively marine,
and include rockweeds, kelp and sargassum.
The brown algae are the largest seaweeds.

22. Marine Invertebrates
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Marine invertebrates are the invertebrates that
live in marine habitats. Invertebrate is a blanket
term that includes all animals apart from the
vertebrate members of the chordate phylum.
Invertebrates lack a vertebral column, and some
have evolved a shell or a hard exoskeleton.

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Sponges: Phylum Porifera
Sponges are filter feeders and the simplest of
multicellular animals. They have no tissues, organs or
nervous system and their cells show little
differentiation and specialization. They are asymmetric
and sessile, and show a variety of growth forms and
colors.

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The phylum Cnidaria is characterized by stinging
cells called cnidocytes, which contain a stinging
organelle called a cnida. The spearing type of cnida,
called nematocysts, can be triggered by touch or
chemical stimulus. They are found mostly in the
tentacles but also in the outer body walls and
gastrodermis. They are used both in catching prey
and in defense.
Cnidarians: Phylum Cnidaria

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Mollusks are a large and varied group of animals that
have a soft body and are most often covered with a
calcium carbonate shell. Their body is divided into two
major parts. The head-foot region includes the head,
mouth, sensory organs and the foot, which is usually
used for locomotion.
Mollusks: Phylum Mollusca

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Arthropods : Phylum Arthropoda
Arthropods are an extremely diverse group; they include
terrestrial insects and represent 75% of all animal species.
Arthropods have an exoskeleton made of chitin, which
provides protection and a point of attachment for muscles.
However this exoskeleton does not grow with the animal,
and arthropods have to molt periodically in order to grow.

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Echinoderms : Phylum Echinodermata
Echinodermata means “spiny skin”. This phylum is a strictly
marine group that includes animals such as urchins, sea
stars and sea cucumbers. They have a complete digestive
tract, and though their larvae show bilateral symmetry,
adults exhibit modified radial symmetry (usually five part
radial symmetry) which allows these slow moving
organisms to respond to stimuli from all directions.