Nichole Morgan
Organism interaction
Final draft
Bio 106 sec
Harp Seal Interactions in the Atlantic
Ecological interactions are affluent on planet Earth, and can be studied on many different
levels. Every ecosystem has unique interactions specific for the environment with which
organisms thrive. Most interactions are fundamentally based upon the needs and wants of an
organism within a given area, therefore the needs determine the interaction put forth. Many
interactions are quite complex while others may be fairly simple. The diversity of every
interaction leads to great wonder, and increased insight of the world we live in. Whatever the
case, organismal interaction is unique and interesting when studied.
The ecological interactions that will be exposed in this paper are fundamentally depicted
within the Atlantic Ocean. The diversity of communities endogenous to the Atlantic are rather
abundant. Results from an extensive quantitative sampling of deep-sea communities indicate a
greater diversity of species than what was previously thought (Grassle & Maclolek, 1991).
Information from the sampling indicates an almost endless amount of interactions that have yet
to be studied. As well, many ecological relationships have enormous impacts on the environment
they comprise themselves within, but also the external environments they are not “truly” part of.
One such instance related to this problem includes the economies of many coastal communities.
The three organisms analyzed in this paper allude to a problem coastal economies face, the
market for fresh fish and seafood.
The harp seal (Phagocillus greolandicus) “Ice-lover from Greenland” is a carnivorous
mammal within the family Phocidae, the family with no true ears. Recently the harp seal has
acquired its own genus due to reasons not being closely related to any other marine mammal
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(Wilson & Reeder, 2005). Harp seals live in various areas spread widely throughout the North
Atlantic and Arctic Ocean. Their range spreads from the northern Hudson Bay and the Foxe
Basin, Baffin Island, the Davis Strait, the Gulf of St Lawrence and Newfoundland in the western
North Atlantic, east to somewhat south of Greenland, continuing east to Iceland and from there
to Northern Norway, the White Sea and the Barents and Kara Seas (Lavigne and Kovacs 1988,
Rice 1998, Lavigne 2002). As semi-aquatic marine mammals, harp seals spend little time on land
and more time in the cold Atlantic waters. Interestingly, harp seals can be submerged under
water for up to fifteen minutes before needing air. Lowering their heart rate by ninety percent
allows harp seals to interact underwater for extended periods of time, something that many other
mammals cannot do. Their ability to remain under water allows for increased hunting time,
making it easier for the seals to graze among just about anything prey they can clench their teeth
into. On that note the next organism discussed is one of the harp seal’s primary food sources.
The Atlantic Cod Gadus morhua (Linnaeus, 1758) are one of the most popular food
fishes in the western world primarily because they live longer and are greater in size than those
from the Pacific Ocean. Atlantic cod thrive in stretches from Greenland to North Carolina, as
well as off the coast of Iceland and along the shores of Europe. Cod are omnivores meaning they
feed on variety of different invertebrates smaller fish and plant or algal material. One of the
primary concerns with this species is the diminishing population size over the past decade. The
drastic change is increasingly affecting many coastal economies of the North East United States.
Atlantic Cod were once the most prevalent predators for many small organisms, due to their
decline a large expansion of prey has become commonplace.
Often times when people think of organisms as being prey the prey are usually much
smaller or weaker than their predator, but this can be proven false. The third organism we will
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discuss in this paper is a blood vessel invading fungi that results in blood clotting of the
organism in which it lives. Entomopthora are fungi that cause a group of infections known as
zygomycosis. Zygomycosis is a pulmonary disease, which is any abnormal condition of the
respiratory system. Mucor, and Rhizopus, examples of infectious agents, induce granulomatous
reactions in the host involving the lungs and the bronchial, mediastinal, and mesenteric lymph
nodes. Dissemination to other vital organs (e.g., kidneys liver, and brain) frequently occur as
well. (Beran, 1994).
The true question posed is how interactions between these three organisms in their cold
Atlantic environment take place. All fungi are hetero-tropic, meaning they cannot produce their
own food, much like plants, which use the process of photosynthesis. Entomopthora is a parasitic
fungi, essentially meaning it absorbs its nutrients from a host organism. The organism in point
being Harp seals. Harp seals are commonly affected by Entomopthora, the parasitic fungi invade
the blood vessels of the seal causing clots within the blood stream. The blood clots however are
not stationary, instead they emobolize, or move through the blood eventually causing the tissue
around the area of the fungi to die. The fungi can be extremely hazardous to many seals.
Zygomycosis is not a contagious disease, infections arise from the inhalation, ingestion, or
inoculation (through trauma) of infectious elements into the body (Beran, 1994). Often seals are
hunted for their white coats at young ages, the sport of hunting can ultimately lead to trauma for
the young pups, prime real estate for zygomycosis to set in.
An ecological interaction that is more obvious than the parasitic fungi within the harp
seal, are the interactions between seals and Atlantic cod. Atlantic cod are prey for harp seals,
causing decreases in the populations of cod. As stated earlier harp seals prey on many fish and
invertebrates within the water where they live. Traditionally harp seals were considered to be
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primarily near shore species. However based on information like catch statistics and tag returns
that were biased towards near shore areas, recent studies have indicated that harps seals are also
present in offshore waters (Stenson, Hammill & Lawson, 1997). This is particularly important
because Atlantic cod are located further offshore.
Harp seal populations have increased from 2.5 million in 1981 to approximately 4.8
million in 1994 (Stenson, Hammill & Lawson , 1997). This massive increase has lead to the
deprivation of many Atlantic cod species that scientists believe cannot be restored. If the cod
populations cannot be restored the market for the health supplement, cod liver oil will decline as
well as the economic markets of many coastal towns where cod, renowned for their flaky texture
are sold.
Though a controversial argument, harp seals are blamed for much of the decline of
Atlantic cod species, the question is, are they the culprits, or perhaps something else? Humans
are involved in many ecosystems on Earth often times disrupting what would otherwise be the
natural flow of things. For example there was a time when harp seal populations were extremely
low because of over hunting. From 1997-1999 465,000 seals were killed, much more than
breeding populations could keep up with. The reason? Most often seals are hunted and killed for
their luxurious pelts worth large quantities of money. With dramatic decreases in seal
populations there should have been an increase in cod populations, although this was not the
case. Due to the demand for seal pelts, the reduction of seal hunts will not decrease anytime
soon. Thus the blame for the loss of Atlantic cod populations should be looked into further.
Harp seals, along with many other sea-mammals, are continuously being accused for dips
in fish populations, however the cost of overfishing is much more dramatic than the natural
predator prey relationship.
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Overfishing is a major problem in the United States as well as around the world. Because
fish are one of the primary predators in the oceans, overfishing decreases the number of
predators thus inversely affecting prey populations. A common example of this is the over
abundance of phytoplankton. Phytoplankton populations have become increasingly more
prevalent than previous years, the increase of phytoplankton has caused an overall increase in
nitrogen levels within the oceans where overfishing is occurring. Nitrogen is important due to its
control of the rate of photosynthesis. However, lack of nitrogen in aquatic ecosystems can inhibit
plant growth. On the other hand an overabundance of Nitrogen can be quite harmful. Plants and
diatoms prefer ammonium and nitrate. Influxes in these forms of nitrogen from sewage,
fertilizer, and animal waste typically cause plant and algae production to increase, leading to
long term fluctuations in dissolved oxygen that may limit sensitive fish and aquatic life
(Schlesinger, 1997).
For the most part harp seal populations have remained steady for the past few years while
Atlantic cod are continuously dying off, possibly near extinction. Not only is this detrimental to
the seals, who depend partially on the cod as a food source, but for many families and businesses
that utilize Atlantic cod for its monetary value. Cod’s importance as a common health
supplement, cod liver oil is a large business. Other sea mammals and harp seals should not be
blamed for the continually decreasing cod populations, when it is evident overfishing causes
most if not all of the damage. Natural ecological interactions between seals and cod pre-over
fishing have not caused near extinction to fish populations. Simply put, to point the finger at
seals seems trivial when the real problem lies within the disruptors of the Atlantic Ocean
ecosystem.
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Ecological interactions on Earth are necessary. Every interaction has its purpose, and its
reason for being. Interactions between organisms are essential for ecosystems to maintain
equilibrium. Factually, humans affect most ecosystems more than any other organism, and thus
are often the culprit of the extinction of a species. It is evident that it is our role as humans to pay
attention and study ecological reactions so we can preserve organisms and the environment.
Humans have needs too, but the eradication of a population due to our interference can hinder
our health as well as other organisms’. Many more interactions exist and have yet to be studied,
but as they are revealed they should also be protected and preserved.
Works Cited
Beran, G. W. (1994). Handbook of zoonoses section a: Bacterial, rikettsial, chlaymidyal, and
mycotic. (2nd ed., p. 501). Boca Ratton: CRC Press.
Grassle F., & Nancy , M. (1991). Deep-sea species richness: Regional and local diversity
estimates from quantitative bottom samples. The American Naturalist, 132(2), Retrieved from
http://www.jstor.org/stable/10.2307/2462414
Schlesinger, W. H. 1997. Biogeochemistry: An Analysis of Global Change. Academic Press,
New York. A classic college to graduate-level text on all things related to movement of nutrients
in ecosystems.
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Stenson, G. B., Hammill, M. O., & Lawson , J. W. (1997). Predation of harp seals in atlantic
canada: Preliminary consumption estimates for arctic cod, capelin, and atlantic cod. Northwest
Atlantic Fish Association, 22, 137-154. Retrieved from http://journal.nafo.int/J22/Stenson.pdf
Wilson, D. E., & Reeder, D. M. (2005). Mammal species of the world; a taxonomic and
geographic reference . (3rd ed., Vol. 2). Baltimore : Johns Hopkins University Press.
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