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Science-Pacific Region-Ocean Sciences-Research Activities |
Plankton Productivity |
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Science-Pacific Region-Ocean Sciences-Research Activities |
Plankton Productivity |
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Zooplankton Laboratory
Animals shown here are ones that we commonly find in the Northeast Pacific Ocean, off the British Columbia coast, as shown on the map to the right.
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Pacific euphausiid, Euphausia pacifica, length to 24 mm / 1". Euphausiids, also known as "krill", are a taxonomic order of crustaceans, separate from the crustacean order of decapods (Shrimp and Crabs). Krill are a major food source for adult fish, seals, whales and birds. After Copepods, they are the most important Zooplankton group in the world oceans. Larval and immature fish feed on the smaller juvenile euphausiids. Krill live in the dark, at 100 metres or more by day. Many adults migrate diurnally to the surface at night, to feed on the phytoplankton. Most are herbivorous, but some are omnivorous feeders. Two species most likely to be found in Georgia Strait, San Juan Archipelago, and Puget Sound, are Euphausia pacifica and Thysanoessa rachii. Off the West coast of Vancouver Island the most common are Euphausia pacifica and Thysanoessa spinifera. |
Copepod, Euchaeta sp., with egg sac, length to 12 mm / 0.5". The largest number of individual Crustacean Zooplankton in the ocean are from this class. Because most of these are small (less than 8 mm), they form a large part of the diet of larval fish. Many are parasites, and therefore carnivores. Most are herbivores. Like most crustaceans and arthropods, copepods have an exoskeleton (external skeleton) and jointed appendages and body segments. A copepod's body is made up of several jointed segments, which each have one pair of legs. They also have one pair of short antennae and one pair of very long antennae. They use their 'legs' to propel themselves through the water in short rapid jerks. |
Chaetognath, Arrow worm, Sagitta sp.,
length to 75 mm .
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Polychaete 'many bristles' worms may reach more than 4 cm (1.5") in length. Polychaetes are a class of Annelids that are generally benthic; however, species of two pelagic families occur in B.C. coastal waters: Tomopteridae and the Typhloscolecidae. The length of these carnivorous worms can vary from less than 5 mm to more than 4 cm. Polychaetes have paddle-like appendages called parapodia on either side of their body that they use either to swim or burrow with. Polycheates vary in shape from sedentary tube worms to free moving planktonic or benthic forms and can feed either passively or actively. Pelagic (free swimming) polycheates tend to be transparent to minimize predation. |
Amphipod, local length to 15 mm / 0.6". Amphipods are mostly marine and can be either benthic or pelagic, but there are some freshwater and terrestial species. Amphipods range in size from under 1 mm to 14 cm, with most of the ones we catch in the 10-15 mm length range. Most amphipods are detritus feeders or scavengers and feed by filtering water or sediment through their appendages; some amphipods many supplement their diet by catching small animals, but strictly predacious feeding is uncommon. |
Sea gooseberry, Pleurobrachia bachei, bell diameter to 20 mm (¾'), tentacle length to 160 mm (6'). Commonly called "Sea goose-berries", or "Comb jellies", these carnivorous ovoids, have eight rows of comb-like swimming appendages around their circumference, called cilia. The two contractile tentacles contain colloblasts (similar to Jellyfish nematocysts, but no stinging cells) that secrete a sticky substance which entangles the prey. The tentacles then contract and pass food up to the mouth. Ctenophores may emit a bright green biolumenesence when disturbed. |
Salp Chain, Individual salps about 10 cm (4") long, chains to 5 m (15') long .
Thaliaceans, or
salps, are a class of tunicates that are specialized for a free-swimming, planktonic
existance. These animals pump water through their body for respiration, feeding, and locomotion. There are only 6 genera of salps and all are
transparent. |
Jellyfish, Moon Jellyfish, Aurelia aurita,
diameter up to 32 cm / 13". Jellyfish belong to the Cnidarian phylum,
which also includes corals, sea anemones, and
hydrozoans. Cnidarians actually have two different
phases of life, the medusa stage
('jellyfish' form, separate sexes) and the
polyp stage (e.g., sea anemones,
combined sexes, picture lower right). Different
classes of cnidarians spend different proportions
of their lives in the medusa and/or polyp stages,
but sexual reproduction can only occur in the medusa
stage.
Asexual reproduction can occur by 'budding' or 'dividing'
of the polyp stage. |
Shrimp and prawns use thier pleopods (found on the abdominal segments) to swim or move along the sea floor, but can also flex their abdomen and use their tail in an escape response. Species living above 500 m are often transparent or semi-transparent; those living deeper than 500 m are often red in colour. Most shrimps are bottom dwellers (benethic) and use their legs for crawling and swimming amongst rocks and plants. Some shrimps are burrowers and use their pleopods to excavate. Samples in our plankton nets vary from under 5 mm (juveniles) to over 5 cm (adults). In Canada, commercially sold "Shrimp" are usually hand or machine peeled (shell removed), are about 2 cm (1") long, and are pink or redish-pink in colour. Commercial "Prawns" are usually not peeled, are between 4-10 cm (2-5") long, and can be black, blue, red, pink, or white. In the U.S., "Shrimp" usually refers to Pandalidae of any size. |
Mysids look similar to shrimps and can be up to 3 cm (1.2") in length. Mysids can be found throughout the oceanic water column and are also found in freshwater environments as well. Some mysids feed on small particles which they collect by grooming their body surface, whereas others are predacious on other zooplankton. Some mysids are scavengers. Marine mysids often are found in large swarms and are an important part of many fish diets. Mysids are also called "Opposum shrimp", because of the brood pouch present in all mature females. |
Ostracods superficially resemble bivalves, but are only a few mm (3/16") in length. Ostracods are sometimes called mussel or seed shrimps and are small crustaceans that are widely distributed in the sea and in fresh water. Their body is completely enclosed in a bivalve carapace. Most ostracods are minute, several mm or less in length. Most ostracods are bottom dwelling, but there are a few pelagic species. Ostracods can be carnivores, herbivores, scavengers, and filter feeders. The bivalve Crustaceans in our area are poorly known. Papers in 1930 and 1952, reported thirty-five species, mainly from near Nanaimo, and seven species from Puget Sound. |
Fish Larvae |
Crab Larvae |
Pteropod, 'Winged snails',
such as the
Clione shown here can reach a length of 12 mm
(0.5"). Two members of this family, which are related to snails, |
Cephalopod Larvae: cephalopods include Squid and Octopus; we only catch larval forms in our nets. Larval forms range up to 4 cm (1.5") |
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Their torpedo-like body shape allows them to move quickly throug the water, and the large spines around their mouth (picture right) helps them to grab and restrain their prey. Chaetognaths alternate between swimming and floating. The fins along their body are not used to swim, but rather to help them float. They use the muscles that run the length of their body to dart forward. Only two species are common in B.C. waters, but some deep-water species may be collected in surface tows on
occasion.
Salps secrete a mucous film that runs along the body wall to the esophagus (mouth) collecting particles from the surrounding water to feed on. Salps often form long chains (up to 30 m / 90' ) and feed near the surface. A common predator of salps that is often seen in local waters is the
sunfish, 
There are four different classes within the Cnidarium phylum:
Anthozoa (Sea anemones and corals), Hydrozoa
(Hydroids), Scyphoza (Jellyfish), and Cubozoa
(Box Jellyfish).
Scyphozans and Cubozoans commonly exist in the medusa phase,
whereas Hydrozoans spend about half their time in the medusa
phase. Anthozoans do not have a medusa stage. 
All cnidarians have stinging cells called 'nematocysts' that are located on the tentacles. When something such as a prey item touches a tentacle, thousands of nematocysts (see figure left) 'fire' towards the object in an attempt to stun and retain it. There are three types of nematocysts: a coiled thread that can entangle prey, a barb that can inject toxins into prey, and a sticky thread that will hold onto prey. Most species of jellyfish and anemones have nematocysts that will not harm humans (next time you are at the beach, touch the tentacles of a sea anemone with your finger and you will feel a 'sticky' sensation -- these are the nematocysts attempting to hold onto you). A few species of jellyfish are highly toxic to humans, such as the local Cyanea capillata and the well known Portuguese man-of-war.
Larvae have displayed special locomotive responses to changing environments (such as sainilty and tides), which may help them from being dispersed into the open ocean.The Reptantia in our samples include the pelagic
Galatheid, Munida quadrispina, and larval Zoea and Megalops.
are found in surface layers of the ocean. The shell-carrying Limacina helicina lives on phytoplankton. The shell-less Cleone limacina, or "Sea butterfly", is
carnivorious.
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The class Cephalopoda includes
the Squid, which has an internal shell or 'pen', and
the Octopus, which has no shell. Octopii are usually
found living on the bottom of the ocean, often in
caves or between rocks. In British Columbia, there
are 3 species of octopus, including the commercially
exploited Giant Pacific Octopus (Octopus
dofleini; right), and two non-exploited smaller
species: O. rubescens and O. leiodema.
Octopus spawn in the fall and the eggs hatch in the
spring. Octopus larvae are planktonic for about
two months in the spring before settling on the
sea floor bottom.
