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I found them under reefs in Fiji. The hand-like structures moved slowly. I was not sure if it was an animal or plant. I was not even sure if they were several individuals or it was a whole. The part that was not hidden by the stone was about 50cm length. I did not touch them, since I was not sure if it was dangerous.
It is probably Holothuria leucospilota
Holothuria leucospilota is a medium-sized sea cucumber reaching a length of up to 40 centimetres (16 in) when relaxed but it can stretch to about a metre (yard) when extended.
Holothuria leucospilota is found in shallow water along the east coast of Africa and in much of the Indo-Pacific region. It is a common species on the north east coast of Australia where it is found on reefs and rocky coasts, often partly concealed under a boulder.
Aquatic organism definition
Aquatic organism" means and includes, but need not be limited to, finfish, mollusks, crustaceans, and aquatic plants which are the property of a person engaged in aquaculture.
Aquatic organism shall mean an individual member of any species of fish, mollusk, crustacean, aquatic reptile, aquatic amphibian, aquatic insect, or other aquatic invertebrate.
Aquatic organism passage is not impaired by road stream crossings except where barriers are necessary to protect native species from invasion by nonnative species.Desired Condition AQ-16.
Aquatic organism passage is improved in forest priority watersheds.
To receive maximum points, a land protection component must be part of the project proposal. A rare resource (natural community or threatened or endangered plant or wildlife) will benefit. Aquatic organism passage is improved preferably goes from non-passable to fully passable by all organisms. Number of stream miles connected is maximized.
Researchers in evolutionary biology, conservation biology, and general organismal biology studies advanced undergraduate and graduate students in biology courses specializing in evolution, general biology, and general life sciences
Introduction: Missing-link: When an "outmoded term", holds "in between features" between the ancestors and its descendants
1. The transitional features of "Missing-link" illuminate the molecular nuts and bolts of biological evolution
2. If and When Evolution is Ultimate Essence of Life: What is the Evolutionary Identity of the Missing-link (resembling Archaeopteryx )
3. Walking with Cynodont to Explore the Uncharted Evolutionary Trail of Mammalian lineage diverged out of Reptilian
4. One Small Step for Amphibious Fish, One Evolutionary Leap for Moving Tetrapods on Earth
5. Evolutionary Origin of Amniotic Egg: The Transitional Form between Amphibians and Reptiles in the Doubt Clear Session
6. When Contemporary Discoveries Pushes the Bony-fish to Ancestral or Evolutionary Back-seat and Discreetly Pushes Cartilaginous-fish in the Advanced or Front-seat
7. Hemichordates: The Bilaterian lineage (also known as phylum- Deuterostome) in the evolutionary crossroads of developmental biology
8. Cambrian Evolution of Onychophorans: In the evolutionary labyrinth of Arthropods, Annelids, and Molluscs
9. The extent of Ctenophore uniqueness - distinctly recognized to be "quasi-Cnidarians" or "stunted Bilaterians"
10. The Protistan Link in Transition: Down the Evolutionary Trail from Unicellular-Protozoa to Multicellular-Metazoa
11. Evolutionary Mysticism of Euglena: A Sagacious Soul of a Plant in the Body of an Animal
12. Virus: A Stepping Stone in Transition in the course of Evolutionary Journey from the World of "Non-Living" to the World of "Living" Entity
13. Once there was an ancestor between humans and apes: In the Quest for the enigmatic Missing-link
14. Mitochondrial Eve and Y-Chromosomal Adam on Planet Earth: Humanity’s metaphoric Missing-link between Prehistoric Past and Contemporary Present
Conclusion: Missing-link: In Search of Our Distant Cousins Footprints, a Quest for Our Evolutionary Journey to the Past
Careers in Aquatic Biology
UCSB's Aquatic Biology majors, because their education is sound, comprehensive, and unique, are in demand in both government and private industry. Aquatic Biology majors secure positions working on biological surveys and environmental impact statements. They pursue careers in the conservation of marine and other resources, gain employment with fisheries, and undertake work in areas such as aquaculture and water quality control. In addition to immediate career entry, Aquatic Biology majors are prepared for graduate study in advanced and specialized fields.
Students interested in teaching biological sciences and conducting research at the college or university level should plan to complete the PhD degree. Teaching at the junior high or high school (secondary) level requires the California single subject teaching credential. Students considering this last option should discuss their plans with the credential advisor in UCSB's Graduate School of Education early in their academic careers.
Estuaries: Where the Ocean Meets Fresh Water
Estuaries are biomes that occur where a source of fresh water, such as a river, meets the ocean. Therefore, both fresh water and salt water are found in the same vicinity mixing results in a diluted (brackish) saltwater. Estuaries form protected areas where many of the young offspring of crustaceans, mollusks, and fish begin their lives. Salinity is a very important factor that influences the organisms and the adaptations of the organisms found in estuaries. The salinity of estuaries varies and is based on the rate of flow of its freshwater sources. Once or twice a day, high tides bring salt water into the estuary. Low tides occurring at the same frequency reverse the current of salt water.
The short-term and rapid variation in salinity due to the mixing of fresh water and salt water is a difficult physiological challenge for the plants and animals that inhabit estuaries. Many estuarine plant species are halophytes: plants that can tolerate salty conditions. Halophytic plants are adapted to deal with the salinity resulting from saltwater on their roots or from sea spray. In some halophytes, filters in the roots remove the salt from the water that the plant absorbs. Other plants are able to pump oxygen into their roots. Animals, such as mussels and clams (phylum Mollusca), have developed behavioral adaptations that expend a lot of energy to function in this rapidly changing environment. When these animals are exposed to low salinity, they stop feeding, close their shells, and switch from aerobic respiration (in which they use gills) to anaerobic respiration (a process that does not require oxygen). When high tide returns to the estuary, the salinity and oxygen content of the water increases, and these animals open their shells, begin feeding, and return to aerobic respiration.
Marine ecosystem Edit
Marine ecosystems, the largest of all ecosystems,  cover approximately 71% of the Earth's surface and contain approximately 97% of the planet's water. They generate 32% of the world's net primary production.  They are distinguished from freshwater ecosystems by the presence of dissolved compounds, especially salts, in the water. Approximately 85% of the dissolved materials in seawater are sodium and chlorine. Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. 
Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides in this figure it is termed the littoral zone. Other near-shore (neritic) zones can include estuaries, salt marshes, coral reefs, lagoons and mangrove swamps. In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.
Classes of organisms found in marine ecosystems include brown algae, dinoflagellates, corals, cephalopods, echinoderms, and sharks. Fishes caught in marine ecosystems are the biggest source of commercial foods obtained from wild populations. 
Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution, climate change, and building on coastal areas. 
Freshwater ecosystems cover 0.78% of the Earth's surface and inhabit 0.009% of its total water. They generate nearly 3% of its net primary production.  Freshwater ecosystems contain 41% of the world's known fish species. 
There are three basic types of freshwater ecosystems:
- : slow moving water, including pools, ponds, and lakes. : faster moving water, for example streams and rivers. : areas where the soil is saturated or inundated for at least part of the time. 
Lake ecosystems can be divided into zones. One common system divides lakes into three zones (see figure). The first, the littoral zone, is the shallow zone near the shore. This is where rooted wetland plants occur. The offshore is divided into two further zones, an open water zone and a deep water zone. In the open water zone (or photic zone) sunlight supports photosynthetic algae and the species that feed upon them. In the deep water zone, sunlight is not available and the food web is based on detritus entering from the littoral and photic zones. Some systems use other names. The off shore areas may be called the pelagic zone, the photic zone may be called the limnetic zone and the aphotic zone may be called the profundal zone. Inland from the littoral zone, one can also frequently identify a riparian zone which has plants still affected by the presence of the lake—this can include effects from windfalls, spring flooding, and winter ice damage. The production of the lake as a whole is the result of production from plants growing in the littoral zone, combined with production from plankton growing in the open water.
Wetlands can be part of the lentic system, as they form naturally along most lake shores, the width of the wetland and littoral zone being dependent upon the slope of the shoreline and the amount of natural change in water levels, within and among years. Often dead trees accumulate in this zone, either from windfalls on the shore or logs transported to the site during floods. This woody debris provides important habitat for fish and nesting birds, as well as protecting shorelines from erosion.
Two important subclasses of lakes are ponds, which typically are small lakes that intergrade with wetlands, and water reservoirs. Over long periods of time, lakes, or bays within them, may gradually become enriched by nutrients and slowly fill in with organic sediments, a process called succession. When humans use the watershed, the volumes of sediment entering the lake can accelerate this process. The addition of sediments and nutrients to a lake is known as eutrophication. 
Ponds are small bodies of freshwater with shallow and still water, marsh, and aquatic plants.  : 460 They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film.  : 160–163 The size and depth of ponds often varies greatly with the time of year many ponds are produced by spring flooding from rivers. Food webs are based both on free-floating algae and upon aquatic plants. There is usually a diverse array of aquatic life, with a few examples including algae, snails, fish, beetles, water bugs, frogs, turtles, otters and muskrats. Top predators may include large fish, herons, or alligators. Since fish are a major predator upon amphibian larvae, ponds that dry up each year, thereby killing resident fish, provide important refugia for amphibian breeding.  Ponds that dry up completely each year are often known as vernal pools. Some ponds are produced by animal activity, including alligator holes and beaver ponds, and these add important diversity to landscapes. 
The major zones in river ecosystems are determined by the river bed's gradient or by the velocity of the current. Faster moving turbulent water typically contains greater concentrations of dissolved oxygen, which supports greater biodiversity than the slow-moving water of pools. These distinctions form the basis for the division of rivers into upland and lowland rivers. The food base of streams within riparian forests is mostly derived from the trees, but wider streams and those that lack a canopy derive the majority of their food base from algae. Anadromous fish are also an important source of nutrients. Environmental threats to rivers include loss of water, dams, chemical pollution and introduced species.  A dam produces negative effects that continue down the watershed. The most important negative effects are the reduction of spring flooding, which damages wetlands, and the retention of sediment, which leads to loss of deltaic wetlands. 
Wetlands are dominated by vascular plants that have adapted to saturated soil.  There are four main types of wetlands: swamp, marsh, fen and bog (both fens and bogs are types of mire). Wetlands are the most productive natural ecosystems in the world because of the proximity of water and soil. Hence they support large numbers of plant and animal species. Due to their productivity, wetlands are often converted into dry land with dykes and drains and used for agricultural purposes. The construction of dykes, and dams, has negative consequences for individual wetlands and entire watersheds.  Their closeness to lakes and rivers means that they are often developed for human settlement.  Once settlements are constructed and protected by dykes, the settlements then become vulnerable to land subsidence and ever increasing risk of flooding.  The Louisiana coast around New Orleans is a well-known example  the Danube Delta in Europe is another. 
Aquatic ecosystems perform many important environmental functions. For example, they recycle nutrients, purify water, attenuate floods, recharge ground water and provide habitats for wildlife.  Aquatic ecosystems are also used for human recreation, and are very important to the tourism industry, especially in coastal regions. 
The health of an aquatic ecosystem is degraded when the ecosystem's ability to absorb a stress has been exceeded. A stress on an aquatic ecosystem can be a result of physical, chemical or biological alterations to the environment. Physical alterations include changes in water temperature, water flow and light availability. Chemical alterations include changes in the loading rates of biostimulatory nutrients, oxygen-consuming materials, and toxins. Biological alterations include over-harvesting of commercial species and the introduction of exotic species. Human populations can impose excessive stresses on aquatic ecosystems.  There are many examples of excessive stresses with negative consequences. Consider three. The environmental history of the Great Lakes of North America illustrates this problem, particularly how multiple stresses, such as water pollution, over-harvesting and invasive species can combine.  The Norfolk Broadlands in England illustrate similar decline with pollution and invasive species.  Lake Pontchartrain along the Gulf of Mexico illustrates the negative effects of different stresses including levee construction, logging of swamps, invasive species and salt water intrusion. 
An ecosystem is composed of biotic communities that are structured by biological interactions and abiotic environmental factors. Some of the important abiotic environmental factors of aquatic ecosystems include substrate type, water depth, nutrient levels, temperature, salinity, and flow.   It is often difficult to determine the relative importance of these factors without rather large experiments. There may be complicated feedback loops. For example, sediment may determine the presence of aquatic plants, but aquatic plants may also trap sediment, and add to the sediment through peat.
The amount of dissolved oxygen in a water body is frequently the key substance in determining the extent and kinds of organic life in the water body. Fish need dissolved oxygen to survive, although their tolerance to low oxygen varies among species in extreme cases of low oxygen, some fish even resort to air gulping.  Plants often have to produce aerenchyma, while the shape and size of leaves may also be altered.  Conversely, oxygen is fatal to many kinds of anaerobic bacteria. 
Nutrient levels are important in controlling the abundance of many species of algae.  The relative abundance of nitrogen and phosphorus can in effect determine which species of algae come to dominate.  Algae are a very important source of food for aquatic life, but at the same time, if they become over-abundant, they can cause declines in fish when they decay.  Similar over-abundance of algae in coastal environments such as the Gulf of Mexico produces, upon decay, a hypoxic region of water known as a dead zone. 
The salinity of the water body is also a determining factor in the kinds of species found in the water body. Organisms in marine ecosystems tolerate salinity, while many freshwater organisms are intolerant of salt. The degree of salinity in an estuary or delta is an important control upon the type of wetland (fresh, intermediate, or brackish), and the associated animal species. Dams built upstream may reduce spring flooding, and reduce sediment accretion, and may therefore lead to saltwater intrusion in coastal wetlands. 
Freshwater used for irrigation purposes often absorbs levels of salt that are harmful to freshwater organisms. 
The biotic characteristics are mainly determined by the organisms that occur. For example, wetland plants may produce dense canopies that cover large areas of sediment—or snails or geese may graze the vegetation leaving large mud flats. Aquatic environments have relatively low oxygen levels, forcing adaptation by the organisms found there. For example, many wetland plants must produce aerenchyma to carry oxygen to roots. Other biotic characteristics are more subtle and difficult to measure, such as the relative importance of competition, mutualism or predation.  There are a growing number of cases where predation by coastal herbivores including snails, geese and mammals appears to be a dominant biotic factor. 
Autotrophic organisms Edit
Autotrophic organisms are producers that generate organic compounds from inorganic material. Algae use solar energy to generate biomass from carbon dioxide and are possibly the most important autotrophic organisms in aquatic environments.  The more shallow the water, the greater the biomass contribution from rooted and floating vascular plants. These two sources combine to produce the extraordinary production of estuaries and wetlands, as this autotrophic biomass is converted into fish, birds, amphibians and other aquatic species.
Chemosynthetic bacteria are found in benthic marine ecosystems. These organisms are able to feed on hydrogen sulfide in water that comes from volcanic vents. Great concentrations of animals that feed on these bacteria are found around volcanic vents. For example, there are giant tube worms (Riftia pachyptila) 1.5 m in length and clams (Calyptogena magnifica) 30 cm long. 
Heterotrophic organisms Edit
Heterotrophic organisms consume autotrophic organisms and use the organic compounds in their bodies as energy sources and as raw materials to create their own biomass. 
Euryhaline organisms are salt tolerant and can survive in marine ecosystems, while stenohaline or salt intolerant species can only live in freshwater environments. 
Lakes and Ponds
Lakes and ponds can range in area from a few square meters to thousands of square kilometers. Temperature is an important abiotic factor affecting living things found in lakes and ponds. In the summer, thermal stratification of lakes and ponds occurs when the upper layer of water is warmed by the sun and does not mix with deeper, cooler water. Light can penetrate within the photic zone of the lake or pond. Phytoplankton (algae and cyanobacteria) are found here and carry out photosynthesis, providing the base of the food web of lakes and ponds. Zooplankton, such as rotifers and small crustaceans, consume these phytoplankton. At the bottom of lakes and ponds, bacteria in the aphotic zone break down dead organisms that sink to the bottom.
Figure 4. The uncontrolled growth of algae in this lake has resulted in an algal bloom. (credit: Jeremy Nettleton)
Nitrogen and phosphorus are important limiting nutrients in lakes and ponds. Because of this, they are determining factors in the amount of phytoplankton growth in lakes and ponds. When there is a large input of nitrogen and phosphorus (from sewage and runoff from fertilized lawns and farms, for example), the growth of algae skyrockets, resulting in a large accumulation of algae called an algal bloom . Algal blooms (Figure 4) can become so extensive that they reduce light penetration in water. As a result, the lake or pond becomes aphotic and photosynthetic plants cannot survive. When the algae die and decompose, severe oxygen depletion of the water occurs. Fishes and other organisms that require oxygen are then more likely to die, and resulting dead zones are found across the globe. Lake Erie and the Gulf of Mexico represent freshwater and marine habitats where phosphorus control and storm water runoff pose significant environmental challenges.
Oceans cover approximately 70% of the earth's surface. Marine communities are difficult to divide into distinct types but can be classified based on the degree of light penetration. The simplest classification consists of two distinct zones: the photic and aphotic zones. The photic zone is the light zone or area from the surface of the water to the depths at which the light intensity is only around 1 percent of that at the surface. Photosynthesis occurs in this zone. The vast majority of marine life exists in the photic zone. The aphotic zone is an area that receives little or no sunlight. The environment in this zone is extremely dark and cold. Organisms living in the aphotic zone are often bioluminescent or are extremophiles and adept at living in extreme environments. As with the other communities, a variety of organisms live in the ocean. Some include fungi, sponges, starfish, sea anemones, fish, crabs, dinoflagellates, green algae, marine mammals, and giant kelp.
Wetlands are environments in which the soil is either permanently or periodically saturated with water. Wetlands are different from lakes because wetlands are shallow bodies of water whereas lakes vary in depth. Emergent vegetation consists of wetland plants that are rooted in the soil but have portions of leaves, stems, and flowers extending above the water’s surface. There are several types of wetlands including marshes, swamps, bogs, mudflats, and salt marshes ([link]). The three shared characteristics among these types—what makes them wetlands—are their hydrology, hydrophytic vegetation, and hydric soils.
Freshwater marshes and swamps are characterized by slow and steady water flow. Bogs develop in depressions where water flow is low or nonexistent. Bogs usually occur in areas where there is a clay bottom with poor percolation. Percolation is the movement of water through the pores in the soil or rocks. The water found in a bog is stagnant and oxygen depleted because the oxygen that is used during the decomposition of organic matter is not replaced. As the oxygen in the water is depleted, decomposition slows. This leads to organic acids and other acids building up and lowering the pH of the water. At a lower pH, nitrogen becomes unavailable to plants. This creates a challenge for plants because nitrogen is an important limiting resource. Some types of bog plants (such as sundews, pitcher plants, and Venus flytraps) capture insects and extract the nitrogen from their bodies. Bogs have low net primary productivity because the water found in bogs has low levels of nitrogen and oxygen.
Effect of the plastic pollutant bisphenol A on the biology of aquatic organisms: A meta-analysis
Frank Seebacher, School of Life and Environmental Sciences A08, The University of Sydney, Sydney, NSW 2006, Australia.
School of Life and Environmental Sciences A08, The University of Sydney, Sydney, NSW, Australia
School of Life and Environmental Sciences A08, The University of Sydney, Sydney, NSW, Australia
Frank Seebacher, School of Life and Environmental Sciences A08, The University of Sydney, Sydney, NSW 2006, Australia.
This research was funded by the Australian Research Council Discovery Grant (DP190101168) to F.S.
Plastic pollution is a global environmental concern. In particular, the endocrine-disrupting chemical bisphenol A (BPA) is nearly ubiquitous in aquatic environments globally, and it continues to be produced and released into the environment in large quantities. BPA disrupts hormone signalling and can thereby have far-reaching physiological and ecological consequences. However, it is not clear whether BPA has consistent effects across biological traits and phylogenetic groups. Hence, the aim of this study was to establish the current state of knowledge of the effect of BPA in aquatic organisms. We show that overall BPA exposure affected aquatic organisms negatively. It increased abnormalities, altered behaviour and had negative effects on the cardiovascular system, development, growth and survival. Early life stages were the most sensitive to BPA exposure in invertebrates and vertebrates, and invertebrates and amphibians seem to be particularly affected. These data provide a context for management efforts in the face of increasing plastic pollution. However, data availability is highly biased with respect to taxonomic groups and traits studies, and in the geographical distribution of sample collection. The latter is the case for both measurements of the biological responses and assessing pollution levels in water ways. Future research effort should be directed towards biological systems, such as studying endocrine disruption directly, and geographical areas (particularly in Africa and Asia) which we identify to be currently undersampled.