David Golowo, Jr.
Literature Analysis Assign.
November 18, 2005
The classic paper that was selected was J.L. Brooks and S.I. Dodson’s 1965 paper
titled “Predation, Body Size, and Composition of Plankton”. This paper studies the
effects of marine planktivore on lake plankton. In it, Brooks and Dodson explain how the
plantivore’s activity affects the size of the plankton, the competition involved for
obtaining plankton, and predation.
First, here is a brief summary of the subject of the paper and a brief synopsis of the
paper itself. Planktons are tiny open-water plants, animals or bacteria. The name, like the
word planet, is derived from a Greek root that means, "wanderer." These organisms range
in size from microscopic bacteria and plants to larger animals, such as jellyfish. Plankton
generally have limited or no swimming ability and are transported through the water by
currents and tides. For example, plankton communities serve as a base for the food
chain.
Plankton can be divided into three major size classes:

phytoplankton–microscopic plants and bacteria

zooplankton–microscopic animals

macrozooplankton–larger fish eggs and larvae and pelagic invertebrates
Plankton are often used as indicators of environmental and aquatic health because of their
high sensitivity to environmental change and short life span. Phytoplankton are useful
indicators of high nutrient conditions due to their propensity to multiply rapidly in the
right conditions. Zooplankton are useful indicators of future fisheries health because they
are a food source for organisms at higher trophic levels, such as finfish. Currently,
research is being conducted in the Chesapeake Bay concerning how plankton react to
different environmental conditions.
A brief synopsis of the classic paper: During an examination of the distribution of
the planktivore in the lakes of southern New England, it was noted that large Daphnia, a
plankton, although present in most of the lakes, could not be found among the plankton
of several lakes near the eastern half of the Connecticut coast. They noticed that there
was great diversity among the plankton in the New England lakes as compared to those in
the Connecticut. These lakes also lacked large zooplankters like Alos pseudoharengus
unlike the lakes in Connecticut which had large numbers of marine planktivore herringlike Alosa pseudoharengus, a marine fish, whose breeding populations have become
established in New York, Connecticut and in the Great Lakes. They introduced into these
diversified New England lakes Alos in 1942 to see how it would affect the planktons.
After 10 years the Alosa became abundant and dominated the Daphnia that had once been
dominant. They theorized that marine planktivore’s predation on planktons affects the
population and survival rate of the planktos. In a lake where there is an abundance of
plankton, the predators ( planktivores ) have a choice of prey size. They prey upon the
larger planktons until they go out of existence. The abundance of the predators allow for
competition among them. The more competition there is among the predators, the more
planktons will be consumed. This results in the shortage of larger sized planktons which
are obvious targets. 1
This paper has influenced other ecologists in their study of plankton and has
helped them better understand how predators prey on planktons based on size among
other factors.
Current areas of research in plankton studies are mainly based on the predation of
the plankton and how predation affects plankton populations. For example, students at the
SERC perform plankton studies where they go on cruises and study free-floating
planktons, both phytoplanktons, and zooplanktons. During a typical cruise, they visit
predetermined stations. At each station they mark the coordinates using the boat’s GPS
units and take the water quality readings using a hydrolab technique. At three of the
stations they obtain plankton samples. They then analyze the plankton samples base on
size and species in the lab and count the species. They also determine the types of
predators that prey on the planktons based on observation of the organisms in the
stations. This information tells them what kind of plankton the predator usually preys
upon, etc. 2
Another study on plankton predation was done by DL Lonsdale of University of
Maryland. In her research, she investigates the planktonic trophic interaction, and has
demonstrated the affects of predation in zooplanktons feeding and population dynamics.3
The last study concerning planktons, their size, habitat, main predators and
competition among these predators was recently done in the Chesapeak
Bay.
An excerpt of the research is shown below:
Unseen by the naked eye, a community of predominantly microscopic
organisms fuels the ecosystem we call the Chesapeake Bay. Plankton include
free-floating microscopic plants (phytoplankton) and free-floating or weakly
swimming animals (zooplankton) that range in size.
These tiny plants and animals drift in the water, largely at the mercy
of the currents and tides. Some of the organisms move up and down in the
water column to take advantage of light. Others will drop below the
pycnocline, a layer where the increase in salinity is more pronounced, to
avoid being washed out to the ocean.
Phytoplankton are the major food source for microscopic animals
called zooplankton. Dominating the zooplankton are the copepods, a group
of tiny crustaceans, about one millimeter long. Zooplankton are distributed
according to salinity levels.
Distribution patterns are also related to those of their main food source, the
phytoplankton. Zooplankton also feed on other particulate plant matter and
bacteria. The tiny larvae of invertebrates and fish are also considered
zooplankton. Although this planktonic stage is only temporary, the larvae
are a significant part of the community. These larvae are consumed by
larger animals, and may, as they grow, consume copepods.
Another group of zooplankton found in the Bay are the protozoa.
These single-celled animals feed on detritus and bacteria. They, in turn,
become food for larvae, copepods and larger protozoa.
Bacteria have an important function in the Bay. They are essentially
the decomposers. Their primary function is to break down dead matter,
particularly plants. Through this process, nutrients in dead plant and animal
matter again become available for growing plants. Bacteria are eaten by
zooplankton and other filter- feeding animals in the Bay.
Bacteria can be residents of the Bay or introduced through various
pathways, including human sewage and runoff from the land. Coliform
bacteria are normal resident bacteria found in the intestines of mammals.
The presence of coliform in a body of water indicates that human or other
animal wastes are present. Coliform bacteria are also an indicator that
disease-producing pathogens may be present in the water.
Clearly visible to the unaided eye, jellyfishes and comb jellies are the
largest zooplankton. Some of these gelatinous creatures swim, though they
are still at the mercy of the water currents. Jellyfishes have tentacles with
stinging cells used to stun prey. The most famous jellyfish in the
Chesapeake is the sea nettle. Sea nettles feed voraciously on zooplankton,
including fish larvae, comb jellies and even small fish. Because of the large
volume of water in their bodies, few animals except sea turtles prey on sea
nettles. Comb jellies, lacking the stinging cells of nettles, capture prey with
adhesive cells. They, too, consume vast quantities of small copepods and
zooplankton, especially oyster larvae. One gallon of Bay water can contain
more than 500,000 zooplankton and one drop may contain thousands of
individual phytoplankton! Here, the cycle of Chesapeake Bay life begins.
Phytoplankton, like algae, are consumed by zooplankton such as copepods.
The copepods are in turn eaten by larval and juvenile fish which are then
consumed by larger fish and wildlife. It is this intricate food web that makes
it possible for you and me to enjoy the succulent and abundant food the Bay
produces.4
References
1. Brooks, JL, Dodson, SI 1965 Predation, body size and composition of plankton. Science 150:
28 - 35
2. SERC “ Student Training in Aquatic Research” www. Serc.si.edu
3. Lonsdale, Darcy J. “ Research Interests” www. Msrc.sunysb.edu
4. Reshetilof, Kathy. “Tiny organisms that determine life in the bay” www.bayjournal.com