Ch. 5 The Microbial WorldCh. 5 The Microbial World

pp.85-100pp.85-100

Size classification ultraplankton - bacteria and other very small plankton,

<5 µm (0.005 mm) nannoplankton - mostly phytoplankton, 5 - 70 µm

(0.005-0.07 mm) microplankton - mostly zooplankton, 70 - 100 µm (0.07

- 0.1mm). Also called "net plankton" macroplankton - not microscopic, for example:

– jellyfishjellyfish

– SargassumSargassum (a type of seaweed that floats at the sea (a type of seaweed that floats at the sea surface)surface)

———————>Size——————> ultra—>nanno—>micro—>macro

Another classification of marine Another classification of marine organisms is:organisms is:

(4) Nekton - Not plankton. Swimming organisms, mostly high trophic level carnivores, but a few are herbivores (e.g.,anchovy). All are heterotrophs.– Examples: fish, squid, marine mammalsExamples: fish, squid, marine mammals

Another classification of marine organisms is:

(5) Benthos - Not plankton. Bottom-dwelling plants and animals. These can be any size and

have any degree of mobility.

Another classification of marine organisms is:

(6) Intertidal and coastal organisms - Not plankton.

Plants and animals often closely related to benthos living in deeper water; some are land organisms adapted to tolerate salt.

Primary producers include seaweeds of coastal areas, sea grasses, mangroves, and other coastal plants

Another classification of marine organisms is:

(1) Phytoplankton - plants, primary producers or autotrophs.

The most important primary producers of the sea.

can grow only in photic zone, but can be found in deeper water.

Most are microscopic algae, and the vast majority are single-celled (unicellular) or colonial (made up of many, identical cells).

2. Major Phytoplankton Groups

2.1 Diatoms 2.2 Dinoflagellates 2.3 Coccolithophores

2.1 Diatoms

CharacteristicsCharacteristics Golden-brown color due to a pigment

fucoxanthin in addition to chlorophyll. frustule (shell-like covering) made of an

organic matrix or framework impregnated with silica (SiO2)

2 basic shapes: centric and pennate

Diatoms

HabitatHabitat Ubiquitous, but most abundant in cold,

nutrient-rich water. Often make up >45% of phytoplankton

biomass in such waters. Often responsible for spring phytoplankton

blooms in temperate and polar oceans. Also abundant in upwelling regions at low latitudes.

Siliceous sediments are often found under regions of high diatom productivity.

2.2 Dinoflagellates CharacteristicsCharacteristics

red or red-brown in color, due to carotene and xanthophyll pigments.

Have flagella, and are motile. (Move vertically in response to light).

Some can absorb organic substances from solution (heterotrophy).

Most have "armor" made of cellulose. Many are bioluminescent (glow, especially

when agitated).

Dinoflagellates

HabitatHabitat Ubiquitous, favor warmer & more

nutrient-depleted water than diatoms.

In temperate regions, often "bloom" in late summer or early fall.

Dinoflagellates Cont. Dinoflagellates and "Red Tides"Dinoflagellates and "Red Tides"

Blooms of certain species of dinoflagellates give reddish or brownish color to the water.

PSP (paralytic shellfish poisoning) or NSP (neurotoxic shellfish poisoning).For example: Gonyaulax and Ptychodiscus are major toxic species in U.S. waters.

Shellfish accumulate toxin as they filter-feed on algae. They are not affected by the toxin. Crabs, shrimp, fish, marine mammals, and humans are affected.

human lethal dose is ~1mg.

Dinoflagellates Cont.

Occurrence and Causes of Harmful Algal Blooms

Worldwide, harmful algal blooms (HABs) appear to be increasing in frequency or duration. Possible causes of increased HABs are:

Excessive nutrient input to coastal due to agricultural fertilizers, sewage

Transport of new species from their habitat to new locations, mostly in ships ballast water

Climatic warming

2.3 Coccolithophores

CharacteristicsCharacteristics

single cells. Covered by plates made of calcite (calcium carbonate)

called coccoliths which make up some calcareous sediments on the sea floor.

2 flagella. Are smaller in size than most diatoms or dinoflagellates.

HabitatHabitat

Dominate in warm, low nutrient, low productivity waters of the oceans.

However, blooms occur in colder waters as well, e.g., Bering Sea since 1997, North Atlantic

Another classification of marine organisms is:

(2) Bacterioplankton - Bacteria– Some are primary producers or Some are primary producers or autotrophsautotrophs: :

– Blue-green "algae" Blue-green "algae" or or cyanobacteria cyanobacteria may be may be responsible for most primary production in responsible for most primary production in some areas of the open seasome areas of the open sea

– Some other bacterioplankton, such as Some other bacterioplankton, such as sulfur sulfur oxidizing bacteria,oxidizing bacteria, are important primary are important primary producers in specific locationsproducers in specific locations

– Some are Some are heterotrophsheterotrophs and decompose the and decompose the remains of dead organisms, excreta, etc.remains of dead organisms, excreta, etc.

3. Bacterioplankton

The most abundant organisms in the ocean (1,000,000 per ml). Have the greatest "standing stock" of biomass in low-productivity regions of the ocean

Another classification of marine organisms is:

(3) Zooplankton - Animals, may be either herbivores (eat plants) or carnivores (eat other animals) or bacteriovores (eat bacteria) or omnivores (eat plants or animals). All are heterotrophs.

Examples: copepods, euphausiids, jellyfish

ZooplanktonZooplankton

HeterotrophsHeterotrophs- - consume organic matterconsume organic matter

– Zooplankton can be: Herbivores, carnivores, detritus Zooplankton can be: Herbivores, carnivores, detritus feeders, omnivoresfeeders, omnivores

– Zooplankton includesZooplankton includes CrustaceansCrustaceans ProtozoanProtozoan Gelatinous zooplanktonGelatinous zooplankton MeroplanktonMeroplankton

1. Crustaceans- include shrimp, copepods, euphausiids ("krill")

Characteristics: Copepods, euphausiids and shrimp superficially resemble one another.

Habitats: Ubiquitous. Euphausiids predominate in the Antarctic Ocean, but are

common in most temperate and polar oceans. Copepods are found everywhere, but are less important in low-

productivity areas of the ocean - the "central ocean gyres". They are found at all depths but are more abundant near the surface.

Role in food webs: Euphausiids and copepods are filter-feeders. Copepods are

usually herbivores, while the larger euphausiids consume both phytoplankton and other zooplankton.

Shrimp are usually carnivores or scavengers.

3. Protozoan - Include foraminifera, radiolarians, tintinnids and "microflagellates" ca.

0.002 mm

Characteristics: Single-celled animals. Forams have calcareous shell Radiolarians have siliceous shell. Both Forams and Radiolarians have spines.

Habitat: Ubiquitous Radiolarians are especially abundant in the Pacific

equatorial upwelling region. Protozoa are especially important components of the food

web in low-productivity ocean areas. Both are found in sediments as well as in the water column.

Role in food web: Feed on small phytoplankton, bacterioplankton, and other protozoans. They can be bacteriovores, herbivores, or carnivores.

4. Gelatinous Zooplankton: includes a variety of fragile, jelly-like organisms which are not closely related

taxonomically.

Cnidarians: jellyfish Habitat: Found everywhere and at

all depths. More abundant in surface waters.

Role in food web: Carnivores, trap prey in tentacles.

Ctenophores: "comb jellies".

Gelatinous Zooplankton:

Salps: A type of tunicate. Characteristics:

Members of the phylum Chordata. Have a complex body structure including internal

organs and a nervous system as larvae but are "degenerate" as adults.

May be solitary or colonial. Habitat: Warm surface waters. Rare at high latitudes. Role in food web: Largely feeds on phytoplankton. A

"ciliary-mucous" filter feeder. Overall: Gelatinous zooplankton are very important,

but little-studied because of sampling problems; they often disintegrate in nets or other sampling devices.

6. Meroplankton Meroplankton are organisms which are part of the plankton for

only part of their life cycle, usually an early, larval stage. As adults the meroplankton are benthos (including intertidal

organisms) or nekton. The meroplankton often do not resemble the adult forms, to

the extent that some were once thought to be separate species.

Meroplanktonic larvae promote survival of the species: Currents carry the offspring to new areas, especially

important for sessile (immobile) benthic animals. Thus, the offspring do not compete with the parents for scarce resources such as food or space. Also, local "disasters" will not wipe out all close relatives.

Meroplankton live in surface waters where food is abundant. Sometimes, the habitat of the adult would not have enough food, especially for a very small organism that could not effectively use the feeding strategy (for example, predation, filter feeding) of the adult.

Meroplanktonic larvae also have disadvantages: Often, reproduction occurs to coincide with

the spring bloom and abundant food. If the spring bloom is not "on time", meroplankton may starve.

Meroplankton are food for the many predators on plankton.

The currents may not carry the meroplankton to an area that provides suitable conditions for adults.

Therefore, organisms which have meroplanktonic larvae usually produce hundreds or thousands of eggs, so that a few will survive.

4. Summary4. Summary (1) Plankton are drifting organisms at the mercy of the currents. (2) There are 3major groups of plankton, phytoplankton, the main primary

producers of the ocean; bacterioplankton, which can be either primary producers or decomposers; and zooplankton, which are animals.

(3) The four major groups of primary producers (autotrophs) in the ocean are:

diatoms, golden-brown algae with siliceous frustules that are commonest in cold, nutrient-rich water

coccolithophores, algae that are covered with small, calcareous plates (coccoliths) and are commonest in warm, tropical waters.

dinoflagellates, red or brown algae that usually have hard coverings of cellulose and are motile by means of a flagellum. They are commonest in summer and fall in the temperate zone of the oceans, and can cause PSP.

cyanobacteria (blue-green algae) are really bacteria that are photosynthetic primary producers, commonest in nutrient-depleted areas of the open ocean.

CopepodCopepod

http://www.bigelow.org/amt/http://www.bigelow.org/amt/copepod.jpgcopepod.jpg

Naupilus LarvaNaupilus Larva

http://http://www.onlineenzyklopaedie.de/www.onlineenzyklopaedie.de/Images/1/180px-naupilus.jpgImages/1/180px-naupilus.jpg

Oyster Trocophore LarvaOyster Trocophore Larva

http://www3.csc.noaa.gov/http://www3.csc.noaa.gov/scoysters/images/bio/lifecycl.gifscoysters/images/bio/lifecycl.gif

Polychaete LarvaPolychaete Larva

http://www.amonline.net.au/http://www.amonline.net.au/exhibitions/beyond/images/400/exhibitions/beyond/images/400/d020.jpgd020.jpg

Horseshoe crab larvaHorseshoe crab larva