Ocean EnvironmentThe sea is the most obvious feature of the earth’s surface. Approximately seventy percent of this surface is covered by water, in one way oranother. Beneath this water are the familiar sands of the beaches, bottoms ofbays, and the inshore ocean. Farther offshore this water covers an amazingsubmarine topography of underwater canyons, trenches, mountains, and plains. Unlike the continents, which are physically separated from one another, theoceans are continuous and interconnected.
Since the “world ocean iscontinuous”(M. J. Keen) it has similar characteristics throughout. In the early1870s oceanographers collected seawater samples from all of the seas of theworld at a variety of depths. When analyzed, the samples were found to havequite similar characteristics.
These findings convinced many that a method ofstudy was needed. The study of oceans was named oceanography. Density, salinity, and temperature are very important concepts in thestudy of oceanography. The salinity and temperature of the water influence itsdensity, and the differences in density are the major factor in understandingthe formation of currents and the positions of water masses in the sea. Inaddition, temperature and salinity play major roles in influencing thedistribution of plants and animals. The sediments of the sea floor may be divided into lithogenous,hydrogenous, biogenous, and cosmogenous sediments.
Lithogenous sediments arethe major sediments on the ocean floor. They are derived from the chemical andmechanical weathering of rocks. Biogenous sediments are composed primarily ofthe protective outter covering of small marine animals and plants. If theseremains comprise at least thirty percent of the sediment it is called an “ooze”.
“Oozes” were named for the types of organisms that formed them. Hydrogenoussediments form as a result of the chemical reactions that occur in the seawater. These reactions result in the formation of small particles, which are depositedon the sea floor. Currents move these particles and cause them to collide withthe other particles.
If many of these collisions occur they may form nodules. Nodules are found on some portions of the deep-sea floor. The sediment typefrequently determines the type of organisms that will be found in that specificarea. “Waves are variable and transitory features of the sea’s surface. “(Sandra Smith) All waves, from the smallest ripple to the most destructivetsunami, have common characteristics. They all have crests, troughs, waveheights, lengths, and periods.
Also, water particles that make up the waves allmove in identical orbital patterns. The orbital pattern is up and forward inthe crest and down and back in the trough. It is only when the wave becomesunstable that the orbital motion is destroyed. The water particles then beginto move at the same speed as the moving wave form.
Breaking waves release a tremendous amount of stored energy on a beachface. This energy moves the sand about and changes the configuration of thebottom. As the bottom configuration is changed by the waves, it changes thecharacteristics of incoming waves. This interaction between the waves and thebottom results in the beach face having an everlasting wave pattern.
Everything in the universe is composed of extremely small paritclescalled atoms, which are often bonded together to form molecules. Molecules areformed as the result fo the transfer of electrons between atoms. The completeloss and gain of electrons results in the formation of ionic molecules, whichhave completely positive and negative vegions. Unequal sharing of electrons, onthe other hand, characterizes the polar covalent molecules, which have onlypartially positive and negative regions. The equal sharing of electrons resultin the formation of nonpolar covalent molecules, which do not develop chargedregions. Due to the development of charges on ionic and polar molecules,intermolecular attractive forces form between these molecules, intermolecularattractive forces form between these molecules and enable the compounds to existin the solid and liquid state.
Ionic compounds have long-range order and existas solids. Polar covalent molecules are liquids because of their short-rangeorder, while the nonpolar gases do not develop intermolecular attractions and asa result exibit no order. Changes in state are due to a change in the order of compounds. Whenenergy is added, molecular motion increases and intermolecular attractive forcesare disrupted.
This results in the melting of solidsand the evaporation ofliquids. When energy is removed, the molecular motion is decreased, whichincreases the formation of intermolecular attractive forces. This allows vaporsto condense as liquids to freeze. The physical and chemical components of water interact with and affectthe plant and animal life in the sea. The plants, animals, and bacteria thatinhabit a given marine area continually react with, change, and are changed bythe total biotic and abiotic environment.
Light plays a vital role in the sea,since the producers require sunlight as the energy source to convert the low-energy simple plant nutrients into the more complex high-energy molecules thatcan be used by the consumers. The dominant plants of the sea are themicroscopic phytoplankton, while copepods. The copepods are important, sincethey provide the major link in the transfer of energy from the phytoplankton tothe large animals of the sea. Density exerts profound effects on both the biotic and abioticcomponents of the sea. Many marine forms, both animal and plant, have developedunique life-styles of seawater. In addition, density barriers are formed in thesea in response to temperature and salinity differences between water masses.
In many cases these density barriers trap nutrients below the euphotic zone andmake them spatially unavailable to the plants in these areas. This is the casein the tropical seas, as well as in all of the world’s deep oceans, where thedensity barriers are permanent. Plant nutrients tend to cycle throughout marine systems, from theirsimple, low-energy, dissolved forms to plants, animals, and then to bacteria. When considering the cycling of nutrients through any system, it is important toremember that metter and energy are inter-changeable. Cycles that encompassboth the biotic and abiotic components of a system are called biogeochemicalcycles.
Biochemical cycles involve the transfer of the essential, minor, andtrace elements from the abiotic to the biotic components of a system. The transfer of food is extremely important in marine life. Thetransfer of food energy may be depicted by food chains and food webs. Foodchains can be and generally are unstable, since the loss of a single link canhave drastic effects on the remainder of the chain. Food webs are more stable,since a variety of alternate food sources exist at each trophic level.
Wind-drift currents are formed by wind moving across the surface of thesea and setting water in motion. Winds are formed by the warning and coolingaffects the density of the air, causing it to move into adjacent air masses. Once in motion, both air and water masses are influenced by the rotation of theearth. This causes the water masses to appear to deflect to their right in theNorthern Hemisphere and to their left in the Southern Hemisphere. As a result,the major wind currents appear to travel in large figure eights from the equatornorthward and southward. Density currents involve a large percent of the sea’s volume.
Sincethese currents are the result of temperature and salinity differentials thatdevelop between adjacent water masses, they are often called thermohalinecurrents. The thermohaline circulation travels through the subsurface waters ofall of the world’s oceans. These currents carry oxygen to the a ysphotic zone,where because of the absence of light, photosynthesis can not occur. They alsoremove large amounts of nutrients from the euphotic zone and transport them forgreat distances throughout the deep ocean. The current patterns in estuaries are also generally formed in responseto density differentials. Depending on the amount of marine and fresh waterthat enters these systems, estuaries may be highly or moderately stratified,vertically homogeneous, or hepersaline.
The resultant salinity variations inthese areas has a direct influence on the biotic distributions in estuaries. Shorelines are the point of contact between the marine and terrestrialenvironments and, as such, are flooded at high tide and exposed at low tide. They are only a part of the coastline or coastal zone, inland and for hundredsof miles along a shoreline. Shorelines are constantly changing.
Coastal sediments are continually attacked and reworked by the sea. Waves move these sediments into the surf zone, where they are picked up andtransported by the the long-shore current. Those sediments are sorted by thiscurrentand eventually deposited to form such major coastal features as barrierislands and sand splits. Inlets form, migrate, close, and reform along barrierbeaches. A combination of inlet fromation, closure, and the overwash of abarrier beach during storms causes the barrier island to migrate towards land.
Estuaries are also major coastal features. They form in a variety ofways. They may form behind a barrier island, sand spit, sea island, or othersuch feature or be formed by the tectonic movements of isostatic adjustments ofthe earth’s crust. Others are formed directly by glacial activity. Estuariesare called a variety of names, including bays, sounds, and lagoons. These arethe most common, but regardless they are all semi-enclosed bodies of water withone or more free connections with the sea.
The construction of groins, jetties and breakwaters is often harmful andtend to cause of increase erosion. All coastlines are extremely dynamic areasthat are interrelated by the longshore currnet. Although these areas must betreated as units, since what occurs along the way will be reflected by beachconditions down the current. The coastal zone provides an unrivaled opportunity to observe ecologicalrelationships. The sea, offshore the inner neritic zone, is remarkable in itsconstancy. In any given area, the salinity and temperature are virtuallyinvariable.
Pressure is constant, but no other environment are the organismssujected to such tremendous pressures. The vast majority of the palagic and benthic realms are in perpetualdarkness, and effective photosynthesis does not occur. All the organisms of theopen ocean are then dependent on the small portion of the sea that is in theeuphotic zone. As a consequence, the animal life is sparce, and different foodchains develop.
In the deep ocean much of the initial energy is thought to beprovided by the bacteria, which like the phytoplankton of the euphotic zone,serves as a food source for the grazers. The second law of thermodynamics, in conjunction with the small areathat is actuall inhabited by the producers, shows the fallacy of relying on thesea as a food supply. It this becomes a reality due to over-population, it willbe necessary to feed at a trophic level much closer to the energy source. Coral reefs are one of the most beautiful and exciting phenomena in theoceans. The coral reef is a biological community consisting of the coral itselfand a variey of small animals and plants, of which algae is as abundant as thecoral. The framework, or base, of the reef is formed by the skeleton of deadcoral animals, with the living corals and algae at the top of the reef.
As thekinds of reef that grow at sea level have to be solid enough to withstand thebattering of the waves, framework must be strong. Many fish and other animalsand plants live on or in reefs, and all this life forms a rich, varied andcolorful community. Coral reefs occur in warm, tropical oceans where the temperature ishigher than sixty-eight degrees farenhiet. They need sunlight in order to grow,so they only grow in clear shallow water down to depths of not much more than ahundred feet. Reefs also need a good circulation of sea water to bring themoxygen and food, so strong wave action is beneficial to them.
Coral is an animal which reproduces very quickly by splitting, to formcolonies of coral. Each animal has a chalky skeleton which is joined toneighboring skeletons, forming the strong framework of the reef. In some coralcolonies, such as brain coral, it is impossible to see each individual animal;but in other colonies, the skeleton of each animal can be seen. Coral feed on zooplankton.
However, the microscopic plants that livewithin the coral also supply it with food and reef-building materials. Theplant in return seemed to benefit from the coral, gaining shelter and foodmaterials from it. There are three main types of coral reefs: the fringing reef, thebarrier reef, and the atoll. Conditions on reefs vary from the breaking surf ofthe sea edge to the quieter lagoon.
The fringing reef grows out from an island,or other land form, but is still attached to it. An example of fringing reefsare the reefs bordering the Florida Keys. A barrier reef is separated from theisland or mainland, and may be a few miles distant. The Great Barrier reef isover a thousand miles long, forming an off-shore break-water for the east coastof Australia. An atoll is a circular surrounding a lagoon, often not associatedwith any obvious land. Atolls occur mainly in the Pacific and Indian Oceans,rising abruptly from the deep seas.
A few centuries ago scientist were puzzled to find coral atolls in thedeep oceans with no land visible because they knew that the corals could onlygrow in shallow. The naturalist Charles Darwin during his voyage on HMS Begalfrom 1831 to 1836, examined the number of atolls and put forth a theory fortheir formation. He suggested that a volcanic or seamount provided a shallowwater base for the growth of the fringing reef. This island would be eroded bythe waves and would sink slowly under its own weight. To remain in shallowwater, the corals of the reef would grow upward as the island sank until thereef became separated from the island by a donut-shaped lagoon, forming a kindof barrier reef.
Further sinking of the island below the sea surface wouldleave only the reef as an atoll, the island being no longer visible. Darwin’s theory was not proven correct until 1952, when holes weredrilled into Eniwetok Atoll in the Pacific Ocean. After drilling through almosta mile of coral, the scientist reached the old volcano. It had been sinking forsome 60 million years and all this time the coral had been growing upwardkeeping pace with the sinking island.
The reproduction of coral is very interesting. During the reproductionstage of the coral, the animal itself is stationed. First and foremost, thepart of the coral that is actually doing the reproducting is called the polyp. Polyps reproduce in two different ways. One is by eggs, and the other is by aprocess called budding. When the egg is fertilezed by sperm, the egg developsinto a tiny larcal organism called a planulae.
The planulae settles on theocean bottom. The planule lands on whatever the currents allow it to. It willmost likely end up on a rock, or on another coral. Eventually the planulaedevelops into a polyp.
Each polyp builds a limestone skeleton which isattached to the surface of which the poyp has landed on, which can be either arock or another coral. After the coral establishes itself, the upper part ofthe body becomes dome-shapes and develops a stomach and a mouth. Tentacles form around the mouth. The tentacles are used to draw food infrom the surrounding waters of the oceans.
the tentacles of teh coral are armedwith special stinging structures. Those special stinging structures are callednematosysts. The tentacle’s nematocysts paralyzes th etiny prey that the coraleats. The coral’s major food are small marine organisms.
In recent years, outbreaks of cholera, typhoid, and viral hepatitis inLatin America, the Mediterranean and Southeast Asia have all been traced tocontaminated seafood. It is because of the discharge of sewage and polutiondirectly into coastal waters. Industrial wastes have been dumped in the oceansof our world. They contain a mixture of chemicals, such lubricating oils, zinc,copper, bleaching agents, and strong acids & alkalis.
These chemicals areextremely toxic to marine organisms. There is strong need for international action to control marinecontamination and pollution. Pollution is now the subject of numerous regionaland international agreements. Conventions regulating the discarge of oil fromships, and the development of emergency response systems to oil pollutionaccidents have contributed to the decline of ship-based souces of oil pollutionover the last two decades.
The moratorium on dumping of radioactive waste atsea under the London Dumping Convention also represents another response toconcerns about the risks posed by such diposal. Some regions have concludedagreement which ban dumping of any radioactive waste at sea. In theMediterranean and Red Sea, all discharge of oily wasted from ships is alsobanned. The differences between terrestial regions are well known. Less wellknown are the features that distingush the Atlantic from the Pacific Ocean, orthe coast of South America from those of Southern Africa.
Regardless of this,the various regions of the world’s oceans are all affected by human activity,with pollution and harvesting of resouces of resouces being common to all seasand oceans. The various marine resources, as well as the extent of humanimpacts on them, are examined region by region, illustrating hos stresses on themarine environmet treatened the very resistance of some habitats and species.
