Explain the reasons why estuaries are extremely productive coastal ecosystems.?
442395
Estuaries are high in nutrients. Lots of plant & animal life which in turn leave organic matter behind when they die. This is great feeding ground for many species which eat dead/decaying material.\n\nB/c of this, estuaries are great "nurseries" for many types of seafood. Fish go to the estuary during spawning. The young grow up there, leave, & return when it is time for them to procreate.
193750
This is due to the seawater having a greater heat capacity than the land, thus they heat and cool off at different rates, causing pressure differentials in the air above them. See the source for details.
169710
You need to refine what you are asking. It is poorly phrased and too broad.\n\nStuarine refers to an esturine environment. Meaning a habitat where freswhwater soruces and seawater soruces meet. Depending on where on the globe you are, you will find a very diverse ecology present at different locations. Many fishes and invertebrates as well as birds utilize these areas for spawning or rearing young. In warmer climates, you will find specialized tree (mangroves) in other areas, seagrasses and other plants. There are also specialized reptiles and mammals associated with stuarine ecology.\n\nPlease come back with additional details and refine the question.
314786
k, the carrying capacity, is measured by population surveys if you assume the population is already at k.  If it's not at k, then you'd have to do some work such as protecting an area against harvest and determining the population of that area every year then determine k for the whole bay based on that.  Actually it's pretty hard to know k in real life, it's more of an abstract guess by ecologists.
819026
Because of the sea salt.
268266
More sunlight, so more rainfall, and plant production, so more animals, so more diversity.
76257
Clear water needn't be clean water (chemically), it only has few solids floating in it.\n\nHow clear water can be depends on a variety of factors.\n\nPlankton: even clear water contains myriads of microbial plankton. Most of it is colourless, but algae have various dyes used for changing light energy into chemical energy. Algae can bloom where the temperatures are right, there are enough nutrients, and there is sufficient light.\n\nClay minerals: Marine sediment as well as riverine detritus contains finely ground minerals which can be stirred up by even slight mechanical force. How much and which grain size can and will be stirred up depends on wave action and sediment make-up. Rocky or large-particle beaches will have clearer water than muddy beaches with the same conditions.\n\nWhat can be blamed on human influence? Mainly the nutrient contents of the water, mostly from agricultural fertilizers and to a somewhat lesser content waste water from settlements or industry. Plus occasional severe cases of extreme pollution like oil etc.\n\nHow clear the water appears is only one of several quality criteria. There won't be many algae in sea water polluted by biocides, but though clear that water won't be pure...
402632
Probably many molluscs would make good environmental indicators (depending on what specific feature you are studying).  Most often I've heard of bivalves being used to indicate heavy metal pollution.  This is likely due to their method of feeding.  (Read more about Bivalves - http://en.wikipedia.org/wiki/Bivalve )\n\nHere is one example of how several molluscs were studied to see which was the best indicator of heavy metals:\n\n"The relationships between concentrations of the heavy metals Pb, Cd, Cu, Zn, Co, Ni, and Ag in nine bivalve molluscs (Arca ventricosa, Chama isotoma: Lithophaga teres. Pinctada margiritifera, Pycnodonte hyotis. Spondylus ducalis. Modiolus auriculatus, Trichomya hirsuta, Ustularca renuta) and their environment were studied."\n\nThere determinations were...\n\n"Accumulation of Pb and Cd by T. hirsuta was linear with time and increased in direct proportion to the external concentration of these metals. No loss of either metal was detected after 12 days in 'normal' seawater."\n\nFrom:  "Investigations of the potential of bivalve molluscs as indicators of heavy metal levels in tropical marine waters"  http://www.publish.csiro.au/nid/126/paper/MF9820285.htm\n\nFrom WikiPedia (in general):\n"Indicator species are unique environmental indicators as they offer a signal of the biological condition in a watershed or ecosystem, and are a warning system that pollution has entered the food web.\nThe term indicator species is a bit misleading, as indicators are often whole groups of flora/fauna types which can be used to assess environmental condition.  Most indicator species are fish, invertebrates, periphyton and macrophytes."\nhttp://en.wikipedia.org/wiki/Indicator_species\n\nCheers!
691491
When the river enters the sea carrying with it a lot of water,  many minerals and chemicals dissolved in it, a large amount of gravel and sand are deposited in the course of the river. The  river spreads into a vast area and and its velocity and force is reduced and a large amount of sand is deposited in the  estuary.  With the accumulation of the sand and the minerals the height of the shore is raised and the river is prevented from entering the sea and stagnates. With the weight of more and more deposits of sand and other particles sediments are formed and block the entrance to sea.
1050409
Some folks are doing interesting things with tidal energy.\n\nIt really all goes back to the sun in the end though - even oil comes from biomas, which captured and stored energy from sunlight.
1140401
well, the diversity of environment, is the fact that there is more than one type of ecosystem on earth, we are not just a desert, or just a rainforest, or plains, or mountains, we have everything.\n\nwithout the diverse nature of our landscape, life would not be possible on the scale that it is.   we would not have the weather systems that heal and renew the scars left by catostrophic weather, and the systems that keep large, dangerous systems in check.\n\ntry the natural georaphic website.
412264
Because it receives the largest amount of rainfall due to the fact that its near the coast. Also, being near the coast allows for the soil to be more fertile, making it more productive for farming.
530231
As a river flows to the sea, it carries huge amounts of sediments from upstream.  These sediments are deposited at the mouth of the river in a fan shaped (triangular) pattern.  Deltas form at the mouth of rivers. Oceans do not have mouths. For example, the Mississippi River delta forms in southern Louisiana where the river ends in the Gulf of Mexico.  The Nile, and the Ganges–Brahmaputra both have large river deltas.\n\nThe delta is a mix of fresh water from the river and salt water from the sea.  Deltas form all over the world, in all climates.  Much of a delta is marshy soil subject to tides and frequent flooding.  This is the habitat for many species of birds, fish, insects, and other animals.  The soil can be very fertile and support a variety of plants and grasses.\n\nTo study the plant and animal life in the delta, pick a particular river, and study it's particular delta.
676507
because sea water has a salt concentration in it, and it is corrosive, similar to an acid but not as destructive. and saltwater will kill plant life harming the surrounding enviroment. they do but they also have salt water filters on the firboats to help bring the salt concentration down.
1058011
I think that what you are asking about might be better called coastal deposition.\n\nOver the span of geologic time the sea level has changed dramatically. As the sea level has moved up and down over time the coastal erosion process has created continental shelves that are covered in deposits eroded from dry land around some continents. This process has also helped shape the coastlines of the continents. \n\nOne of the more spectacular examples of coastal deposition are river deltas. The sediment carried by the river is deposited as the flow of river water slows. This tends to sort the sediments according to the energy level of the water that is flowing into the open ocean. First larger grains like gravel and pebbles settle down, and as the river slows, sand, and finally clay size particles settle out of the water. Many river deltas have built up sediment deposits that are several miles thick and cover areas as large as some states. Most of southern Louisiana is a river delta deposit. \n\nAlong many coasts there is a predominant wind direction that helps to build coast long-shore currents. These currents move parallel to the coastline and will cause sediment accumulations (from rivers) such as sand bars and islands to slowly migrate in one direction. Much of the sand on beaches is actually slowly migrating along the shore. As heavier winter waves move the sand offshore, the sand also tends to move along the shore and sometimes temporarily moves back up onto the beach at a new location. \n\nAnother geologic process that is involved in coastal change is both uplift and subsidence. Uplift is taking place on some coasts due to tectonic plate motion. Other coasts are subsiding, or sinking, due to both faulting and slow compaction of underlying sediments. This sort of subsidence is taking place along the Gulf Coast of the US where there are large growth faults that parallel the coast that are sinking towards the Gulf. Sediment deposited thousands and millions of years ago is still settling in some areas and this leads to loss of coastal wetlands and rising local sea level. \n\nIn other areas coastlines are being changed by local erosion of uplifted sediments (e.g. California). Landslides carry hillsides down to the coastline. Another change in many coastlines is being caused by a geologic process called isostacy. As glaciers accumulated across North America during the last ice age, they weighed down that part of the earth's crust and caused it to sink into the asthenosphere. The glaciers melted long ago, but the areas that were covered by glaciers are still rising. This creates a sort of teeter-totter effect, where some coastlines like parts of the East Coast of the US and the Louisiana coast are sinking. \n\nInformation on isostatic rebound:\nhttp://www.homepage.montana.edu/~geol445/hyperglac/isostasy1/\n\nMississippi River Delta:\nhttp://www.lacoast.gov/geography/basins/mr/\n\nExplanation of long shore drift:\nhttp://www.cofc.edu/CGOInquiry/longshoredrift.htm\n\nGood explanation of barrier islands:\nhttp://www3.csc.noaa.gov/beachnourishment/html/geo/barrier.htm\n\nA very good illustration of differential erosion in a coastal setting:\nhttp://www.rgs.edu.sg/events/geotrip/stack.html\n\nUN Coastal Types:\nhttp://www.oceansatlas.com/servlet/CDSServlet?status=ND0yNzYwJmN0bl9pbmZvX3ZpZXdfc2l6ZT1jdG5faW5mb192aWV3X2Z1bGwmNj1lbiYzMz0qJjM3PWtvcw~~
1069451
the tides are caused primarily by the moon, the gravitational pull of the moon bunces up the surface of the ocean. the sun also afects the tides by adding its gravitation pull when alligned with the moon you have the highest tides. but you are asking about extreme tidal changes. those are usually caused by the shape and epth of the shoreline. a narrow steep bay will have ahigher tide than awide shallow bay
27821
Natural resources\n\nThere is a substantial amount of petroleum and natural gas under the seabed: see North Sea oil.