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Benthic Communities Benthic marine organisms live on or in the ocean floor. There is an enormous variety of benthic creatures. Seaweeds and plants The problem of large marine authotrophs Structure of seaweeds Classification of seaweeds Seaweed communities Vascular marine plants Salt Marshes and Estuaries Rocky intertidal communities Sand Beach and Cobble Beach Communities Coral Reef Communities Coral Animals Other Denizens of the Reef Reef Types The Deep-Sea Floor Vent Communities Whale-Fall Communities The Distribution of benthic organisms Benthic organisms spend nearly all their lives on or in the ocean floor. Their distribution is rarely random; clumped distribution is the most common. The Distribution of benthic organisms, marine station report Population Distribution of benthic organisms A random distribution Clumped distribution Uniform distribution Characteristics of populations - human populacion ecology Characteristics of populations : Each population has its own group of individuals of the same species in a given area : 1. Population size: number of individuals in the gene pool 2. Population density: number of individuals in a given area 3. Population distribution: pattern of distribution (uniform, random, clumped) Age structure: pre-reproductive, reproductive, post-reproductive 5. Reproductive base: those individuals in the pre-reproductive or reproductive stage -------------------------------------------------------------------------------- II. Population Size and Exponential Growth Births and immigration increase population size, Deaths and emigration decrease population size Zero Population Growth (ZPG) = no net increase or decrease Growth of populations over time: For a small population, as long as the birth rate is slightly above the death rate, a population grows exponentially with a characteristic J-curve: Example: population of 2000 mice; 200 die each month, but 1000 are born Birth rate: 1000 born / 2000 = 0.5 (50%) Death rate: 200 die / 2000 = 0.1 (10%) Net change: 0.5 - 0.1 = 0.4 (net growth rate) (40%) After one month: 2000 x 0.4 = 2000 + 800 = 2800 mice! After 2 months: 2800 x 0.4 = 2800 + 1120 = 3920 mice! After 3 months: 3920 x 0.4 = 3920 + 1568 = 5488 mice! After 1 year: 158,726 mice! After 18 months: 1,195,134 mice!...and so on If you plot number of mice per time: J-curve Why is this exponential (or geometric - a curved line) rather than linear (or arithmetic - a straight line)? Every month, the reproductive base gets larger! SEAWEEDS AND PLANTS SEAWEEDS AND PLANTS Multicellular algae Nearshore temperature habitats often include multicellular marine algae: seaweeds. Unlike true plants, the photosynthetically efficient algae lack vessels to conduct sap. The Problems of Large Marine Authotrophs Structure of Seaweeds Blades Stipes Holdfash Gas bladders Thallus Classification of Seaweeds Accessory pigments Phaeophyta – 1,500 living species, kelps genus Macrocystis Rhodophyta Seaweed Communities Vascular Marine Plants Multicellular and unicellular algae. Sea urchins can absorb carbohydrates. Too many urchins can destroy a kelp forest by releasing the kelp from holdfasts. Phyllospadix Mangroves (Phizophora) Not all large marine authotrophs are seaweeds. Some, like the sea grasses and mangroves, are vascular plants. SEAWEEDS Algae Seaweed Prints by M.A.Robinson Algae - wiki Algae Research Mandrove distribution Introduction to the Rhodophyta Phaeophyta Rhodophyta Species Inventory BRACKISH-WATER MOLLUSKS Description and global invasive database of species COMMUNITIES OF SALT MARSHES AND ESTUARIES Salt marsh and seagrass communities COMMUNITIES OF SALT MARSHES AND ESTUARIES Estuary An estuarine marsh Highly productive salt marshes and estuaries shelter a great variety of benthic life-forms and serve as nurseries for some pelagic organisms Life in water Geography: ecosustems TEST OF SALT MARSH AS A SITE OF PRODUCTION AND EXPORT OF FISH BIOMASS Salt marshes are among the most productive ecosystems in the world, and although they are thought to enhance the productivity of open estuarine waters, the mechanism by which energy transfer occurs has been debated for decades. One possible mechanism is the transfer of saltmarsh production to estuarine waters by vagile fishes and invertebrates. Saltmarsh impoundments in the Indian River Lagoon, Florida that have been reconnected to the estuary by culverts provide unique opportunities for studying marsh systems with respect to aquatic communities. The boundaries between salt marshes and the estuary are clearly defined by a system of dikes that confine fishes into a known area, and the exchange of aquatic organisms are restricted to culverts where they may be easily sampled. A multi-gear approach was used to estimate standing stock, immigration/emigration, and predation monthly. Changes in saltmarsh fish abundance, and exchange with the estuary reflected the seasonal pattern of marsh flooding in the northern Indian River Lagoon system. During a six month period of marsh flooding, saltmarsh fishes had continuous access to marsh food resources. Piscivorous fishes regularly entered the marsh via creeks and ditches to prey upon marsh fishes, and piscivorous birds aggregated following major fish migrations to the marsh surface or to deep habitats. As water levels receded in winter, saltmarsh fishes concentrated into deep habitats and migration to the estuary ensued. The monthly estimates of standing stock, net fish migration, and predation were used to develop a biomass budget to estimate the annual production of fishes and the relative yield to predatory fish, birds, and direct migration to the estuary. Annual production of saltmarsh fishes was estimated to be 16.9 g·m-2 salt marsh, which falls within the range of previously reported values for estuarine fish communities. The relative yields were 21% to piscivorous fishes, 14% to piscivorous birds, and 32% to export. Annual export of fish biomass was 5.2 g fish·m-2 salt marsh representing about 1 - 2% of saltmarsh primary production. Saltmarsh fishes convert marsh production to high quality vagile biomass and move this production to the estuary providing an efficient link between salt marshes and estuarine predators Marine and Coastal Systems DFL 04.20.09 Погиб музыкант группы "Любэ" Анатолий Кулешов California''s Rocky Intertidal Zones The following materials are exerpts from the California Coastal Commission''s California Coastal Resource Guide, which can be ordered from University of California Press by calling 1-800-822-6657. Benthic–pelagic links and rocky intertidal communities ROCKY SHORES Anthopleura elegantissima Anemone Clones and Bare Zones Mytilus trossulus Clump Dog Whelk Color Variants Pollicipes polymerus Closeup Inducible Defense of a Barnacle Palm Seaweed Postelsia palmaeformis Surf Grass, Phyllospadix Durvillaea antarctica The "Loco" Concholepas concholepas Biogeographical patterns of rocky, Intertidal Pool Wetland Ecological Models, H.C. Fitz and N. Hughes Ecological models of wetlands are a diverse assemblage of tools for better understanding the wide range of wetland types distributed throughout the globe. However, these models generally share a common characteristic: they are conceptual and quantitative tools that consider the responses of some part of the ecosystem to varying magnitudes and frequencies of flooding. For some purposes, this may be as simple as an assessment of the suitability of specific ranges of water levels for different biological communities. More complex ecological modeling tools may investigate nutrient dynamics with changing surface and ground water flows. Further details in an “integrated” model may link those nutrients to plants and animals within a wetland. Regardless of the model objectives, a principal driver of wetland models involves the hydrology of flooding and associated soil saturation. These wetland physics influence the selection of the ecological processes to be considered in model development. Assuming an introductory level understanding of ecology, this article summarizes the types of ecological models that are used to better understand “natural” wetland ecology. In particular, intermittent flooding is a definitive characteristic of wetlands, and is an important consideration in modeling those systems. Paleontology Biology: Definition of animals Animals are multicellular Except for sponges, animal cells are arranged into tissues. Tissues are necessary to produce organs and organ systems. Tissues, organs, and organ systems enabled the evolution of large, multicellular bodies. Animal cells lack cell walls The cells are held together by protein structures called junctions that extend from one cell to another. An abundance of extracellular proteins also support the cells. A skeleton supports the tissues of large animals. Animals have a period of embryonic development During embryonic development, cells become specialized and tissues form. The growth of tissues, organs, and organ systems therefore requires a period of embryonic development. Animals are heterotrophs Heterotrophs consume their organic food. Except for sponges, they ingest food and digest it in a central cavity. Recall that fungi are also heterotrophs but fungi do not ingest their food. Fungi secrete enzymes into their environment and absorb broken down organic food products. Animals are motile Biology: Animals Biology: Hydra as a model system Biology:BIOLOGICAL DIVERSITY: ANIMALS Biological dispersal - wiki Sand/Gravel/Cobble Shore - SAND BEAC H AND COBBLE BEACH COMMUNITIES Coastal Geomorphology & Habitats Cobble & Bedrock Beach Conifer Swamp Great Lakes Marsh Sand Beach & Open Dunes Wooded Dune & Swale cobble beaches Cobble beaches are formed largely where there is erosion of glacial deposits on islands or on headlands that were left behind by the retreat of glaciers. This includes periglacial and glaciofluvial deposits. Periglacial deposits were laid down adjacent to the margin of the actual glacier. Glaciofluvial deposits of sediment ranging in size from coarse cobbles down to silt were deposited from rivers of water that flowed from a glacier as it melted. Coastal and offshore drumlins provide sediment for beach deposits of cobble. Drumlins are smooth hills of glacial till that were formed during the last ice age. They are 15 to 30 m high and may be longer than a kilometre. From the air they are egg-shaped with the pointed end indicating the direction of the flow of ice that created them. Drumlins are composed of loose stones and boulders of various sizes. Drumlins, by virtue of their composition, are well drained and easily eroded. Shells Coral Reef Animal Printouts Corals That is a coral reef. What is coral? When you see pictures in National Geographic of huge rock like things in the ocean with fish swimming all around, is that coral? Well, sort of. That is a coral reef. Coral is an animal that belongs to the phylum cnidaria. A phylum is a group that scientists place animals in which share certain characteristics. Cnidarians are radially symmetric, which means that they are the same all the way around, 360 degrees! They are built like sacs with a hole in one end that is surrounded by stinging tentacles. Jellyfish are cnidaria. Now, you are probably thinking, jellyfish don''t look anything like what I thought coral was! That''s because the most common pictures of coral are colonies called reefs. During the mating season coral polyp release eggs and sperm into the water (picture below) and when an egg and a sperm meet they form a larva known as a planula. Corals are marine animals of the class Anthozoa, which also includes the sea anemones (order Actiniaria). Corals are gastrovascular marine cnidarians (phylum Cnidaria) and exist as small sea anemone-like polyps, typically in colonies of many individuals. The group includes the important reef builders known as hermatypic corals, found in tropical oceans, and belonging to the subclass Zoantharia of order Scleractinia. The latter are also known as stony corals since the living tissue thinly covers a skeleton composed of calcium carbonate. A coral "head" is formed of thousands of individual polyps, each polyp only a few millimeters in diameter. The colony of polyps function as a single organism by sharing nutrients via a well-developed gastrovascular network. Genetically, the polyps are clones, each having exactly the same genome. Each polyp generation grows on the skeletal remains of previous generations, forming a structure that has a shape characteristic of the species, but also subject to environmental influences. Although sea anemones can catch fish and other prey items and corals can catch plankton, these animals obtain much of their nutrients from symbiotic unicellular dinoflagellates (type of photosynthetic algae) called zooxanthellae. Consequently, most corals are dependent upon sunlight and for that reason are usually found not far beneath the surface, although in clear waters corals can grow at depths of up to 60 m (200 ft). Other corals, notably the cold-water genus Lophelia, do not have associated algae, and can live in much deeper water, with recent finds as deep as 3000 m.[1] Corals breed by spawning, with many corals of the same species in a region releasing gametes simultaneously over a period of one to several nights around a full moon. Corals are major contributors to the physical structure of coral reefs that develop only in tropical and subtropical waters. Some corals exist in cold waters, such as off the coast of Norway (north to at least 69° 14.24'' N) and the Darwin Mounds off western Scotland. The most extensive development of extant coral reef is the Great Barrier Reef off the coast of Queensland, Australia. Indonesia is home to 581 of the world''s 793 known coral reef-building coral species. There are several other types of corals, notably the octocorals (subclass Octocorallia) and corals classified in other orders of subclass Zoantharia: to wit, the black corals (order Antipatharia) and the soft corals (order Zoanthinaria). Extinct corals include rugose corals and tabulate coral. These two groups went extinct at the end of the Paleozoic. Most other anthozoans would be treated under the common name of "sea anemone". Coral Reefs: Coral Plants and Animals corals coral reefs polyp tropical reef-building corals are hermatypic deep water corals - ahermatypic corals Other Denizens of the Reef Reef Types Fringing Reefs Barrier Reefs Atolls Coral reef communities are exceptions to the general rule that tropical oceans are unproductive. Closely cycled nutrients and the specialized dinoflagellates in coral organisms make high productivity, and high species diversity, possible. Other Denizens of the Reef Reef Reef Types Various criteria have been used to classify reefs; the most accepted approach is morphological grouping. The shape and location of reefs are controlled by the bottom topography upon which they formed, interactions among the resident biota, and physical processes. Darwin 1842 discussed three main types of reefs - barrier reefs, fringing reefs and atolls - still part of most classifications today. Fringing reefs occur adjacent to land with little or no separation from the shore. A low input of terrigenous sediment is important, and the best-developed fringing reefs occur off shorelines where rainfall is low, there is little relief, or else the hillsides are stabilized by heavy vegetation. In recent years, clear cutting of forests and poor land management have impacted fringing reefs more than any other type. Barrier reefs are separated from the shoreline by a moderately deep (usually) body of water - the lagoon. The reef may form at the shelf edge, or it may be located more inshore, usually localized on an antecedent break in slope. Atolls are roughly circular in plan with a central lagoon that contains no significant land mass. The central lagoon is often deep (less than 25 m), but this is not a prerequisite. If land does exist, it sits atop a part of the encircling reef and is comprised solely of carbonate material derived from the reef. As originally defined for Pacific reefs, the term implies a specific genetic origin around a volcanic island. Caribbean and Atlantic atoll-like reefs are not of this type, and tend to form around isolated highs formed by local tectonics. A barrier reef is a morphologic entity, separate from its tectonic regime. A limit should be set on lagoonal dimensions in fringing vs. barrier reefs. Implied in Darwin''s definition of reef types is the idea that the lagoon is sufficiently large to permit open circulation behind the reef. The reef serves as a "barrier" that clearly separates lagoonal processes from those of the open ocean. Based on this, we pragmatically make the split between barrier and fringing reefs at a point when the lagoon reaches 500 m in width and 5 m in depth. In a natural setting, and in the absence of significant upland clearing of vegetation, a lagoon of this magnitude can substantially isolate the reef from direct impact by terrestrial runoff. Furthermore, circulation within the lagoon is distinctly removed from that of the open ocean beyond. Classification criteria are summarized in the Table. Other Reefs Patch reefs are smaller features, roughly equant in plan view. While they have generally reached sea level, this is not necessarily so. Usually, patch reefs occur within the lagoon behind the barrier or atoll rim. On occasion, however, they can occur on the open shelf as pinnacles. Modern examples of exposed (i.e. non-lagoonal) patch reefs occur off the north coast of St. Croix in the Caribbean Sea. Numerous small reefs, 10-20 m across, rise out of 10-15 m of water. Their fabric of broken and piled-up coral branches has led to the local name "haystacks". In the fossil record, many of the Silurian reefs of the Michigan and Illinois Basins appear pinnacle-like when viewed in stratigraphic cross section (Fig. 7.9). However, this characterization is largely an artifact of the vertical exaggeration required to fit these sections onto a published page. When plotted at equal horizontal and vertical scales, these reefs appear much broader in cross section. While it is difficult to determine precisely their actual relief at any one time, it is likely that their pinnacle-like character is in large part due to the sequential stacking of one reef atop another. Submerged shelf-edge reefs are Caribbean platform margins that presently sit in water depths greater than 10-15 meters after being flooded by rising sea level 6,000 - 10,000 years ago. Since then, they have not been able to offset the effects of ever-deepening water, and many of them have been left behind. While coral and other calcifying organisms occur along most of these margins, they are not producing carbonate at a rate sufficient for the reef to "catch up" with sea level. Equally problematic are reefs that occur on wider shelves (>5 km), and fall between the criteria for either barrier or patch reefs. They are similar to patch reefs in shape, but they are usually larger, more linear, and are aligned in roughly shore-parallel. They exist near sea level and, in some instances, have shoaled enough that islands can form. The sediments behind the reef (landward) are similar to those seaward reflecting the absence of lagoonal conditions. Because they usually occur along either insular or continental shelves, they are classified as shelf reefs. The nature of shelf reefs changes from shore to the shelf edge. More-seaward reefs are exposed to higher wave energy. Those closer to shore come more under the influence of terrestrial sedimentation. For example, on the southern coast of Puerto Rico, the inner-shelf reefs are often subjected to fine-grained sediments derived from the adjacent hillsides . As a result, they are mostly mud mounds with scattered corals. In some instances, they have been stabilized by mangroves and have built small islands. The mid-shelf reefs are subject to the effects of open-ocean circulation and more wave action. Accordingly, coral cover is higher and the benthic-community structure is more complex. A similar pattern occurs across the Queensland shelf from inner reefs and islands under the influence of heavy runoff to the mid-shelf and outer-shelf reefs that occur in increasingly clearer but rougher water. This is reflected in higher growth rates by the coral Porites lutea at similar water depths along the more-seaward reefs. Isdale, 1984 Paralleling this pattern, photosynthetic species of sponges increase in abundance as the water clears near the shelf edge Reef formation Coral reefs are divided into four main types: fringing reef, platform reefs, barrier reefs and atolls. Reef ecosystem Nontropical Reef Types and Associated Communities -Sea Grass Communities: Florida, Sargass sea Sea grasses are the only flowering plants that live their entire lives completely and obligately in seawater. Forty-five species are known worldwide; six of those occur in Florida, and only three are of major importance. Turtle grass (Thalassia testudinum) is the best known, with its large, ribbon-like leaves that are 4-12 mm wide and 10-35 cm long. Two to five leaves per shoot grow from stout rhizomes that may be found as deep as 25 cm in the sediment. Turtle grass is the major species in the extensive meadows of south and west Florida. Manatee grass (Syringodium filiforme) is commonly found in mixed sea grass beds or in small, dense monospecific patches. Its leaves are string-like: round in cross-section, about 1 mm in diameter and up to 50 cm long. The rhizomes are less robust than those of turtle grass and seldom penetrate as deep into the sediment. The blades of shoal grass (Halodule wrightii) are like thin ribbons, typically 1-3 mm wide and 10-20 cm long, with two or three points. Shoal grass is an early colonizer of disturbed areas Of the 10,000 km2 of sea grasses in the Gulf of Mexico, more than 85 percent occur in Florida waters (Iverson and Bittaker, 1986). Sea grass beds totaling more than 5,500 km2 are found in the warm, shallow waters of Florida Bay and adjacent to the Florida coral reef tract; they cover 80 percent of the sea bottom between Cape Sable, north Biscayne Bay, and the Dry Tortugas. Sea grass cover declines sharply north of this area on both coasts. The shifting sand beaches of the high wave energy Atlantic coast restrict sea grasses to protected bays and inlets. On the Gulf coast, high turbidity and low salinity inhibit sea grass development off the Everglades. Along the southwest coast of Florida, sea grasses are found primarily in bays and estuaries. Extensive meadows of sea grass blanket the broad shallow shelf of the northeastern Gulf in the Big Bend region, from Tarpon Springs to St. Marks. Sargasso Sea Organisms Phytoplancton Exploring the deep ocean floor: Hot springs and strange creatures THE DEEP-SEA FLOOR Most of the deep-ocean floor is an area of endless sameness. It is eternally dark, almost always very cold, slightly hypersaline (to 36%0, and highly pressurized. But there are 4,500 organisms per square meters. There were 798 species recorded in 21 samples in 1980s: a blind tripid fish, abyssal bentic animals such as oneirophanta, holothurian (sea cucumber), apseudes galatheria in the Kermadec trench, oneirophanta. Marine Zoogeography, 1974, from J.C.Briggs. the ooze. The deep-sea floor is the ocean’s most uniform habitat. It is populated by a large variety of highly specialized species. Seafloor geology Following the trail of sand in Monterey Canyon active submarine canyons Ocean explorer Ocean ChEss SciencePlan Deep-sea hydrothermal vents and their associated fauna were first discovered along the Galapagos Rift in the eastern Pacific in 1977. Vents are now known to occur along all active mid ocean ridges and back-arc spreading centres, from fast to ultra-slow spreading ridges. The interest in chemosynthetic environments was strengthened by the discovery of chemosynthetic-based fauna at cold seeps along the base of the Florida Escarpment in 1983. Cold seeps occur along active and passive continental margins. More recently, the study of chemosynthtetic fauna has extended to the communities that develop in other reducing habitats such as whale falls, sunken wood and areas of oxygen minima when they intersect with the margin or seamounts. National Institute of Oceanography (NIO), India Natural Resources Canada Trophic biology Introduction to the oceanography of Monterey Bay and the biology of midwater scyphomedusae Life on the deep sea floor Larger animals Patience Many deep-sea animals including sponges, sea anemones, tube worms and barnacles, adopt a ''sit and wait'' strategy-- staying for long periods, sometimes permanently, in one place and depending on food particles that either fall on to them or are carried to them in the currents. Barnacles project only a few centimetres above the sediment surface. Other sedentary animals raise their feeding structures well above the bottom on long, thin stalks. Vultures of the abyss The amphipods will soon be joined by a number of other active swimmers, including scavenging fish and shrimps, and the sediment around the carcass will be disturbed rapidly by their feeding frenzy. When no suitable food is left, the tiny pieces remaining will attract slow-moving animals, such as molluscs, starfish, brittlestars and sea cucumbers. Finally, bacteria will finish the demolition job, even breaking down bones, so that within weeks of the arrival of the carcass there would be hardly any evidence that it had ever existed. Smaller beasts Apart from when they are brought together by these food bonanzas, animals big enough to be seen with the naked eye are distributed fairly thinly on the deep-sea floor with perhaps one animal every 10 or 20m. But for every one of these big animals there are many thousands of tiny ones, no more than a few millimetres long and living hidden away in the abyssal mud. Many different animal groups are represented here, but just four or five groups dominate in terms of numbers. The very smallest Tiny bacteria cells occur everywhere on Earth where life is remotely possible and their presence in the deep ocean has been known for decades. Until the 1970s, however, just a few rather similar oceanic types were recognised, but new techniques have revealed a bewildering variety in two quite distinct kingdoms, the true Bacteria and a newly recognised one, the Archaea. Recognition of the importance of these organisms in oceanic processes has also grown enormously in recent years. They occur on and within all deep-sea animals, where they perform a variety of crucial roles, ranging from producing bioluminescence to helping with digestion or even providing a source of food themselves. They also live independently of other organisms, being involved in a multitude of chemical processes in the water column and sea-bed sediments, in and around hydrothermal vents, and are associated with natural oil and gas seeps. Bacteria have also been cultured from mud cores collected from hundreds of metres beneath the sea bed in sediments deposited millions of years ago. How they survive in this unbelievably hostile environment is still something of a puzzle, but the discovery of this deep biosphere is potentially enormously important. It suggests that tiny microbes may inhabit vast regions of the Earth''s interior, way beyond the reach of any other life-forms. If so, despite their diminutive individual size the Bacteria and Archaea may in combination outweigh all the rest of the planet''s living organisms put together. Unravelling the mysteries of this new-found, but ancient, world will be one of the great challenges to ocean scientists in the twenty-first century. Marine biogeography and ecology Although biogeography and ecology had previously been considered distinct disciplines, this outlook began to change in the early 1990s. Several people expressed interest in creating a link that would help ecologists become more aware of external influences on communities and help biogeographers realize that distribution patterns had their genesis at the community level. They proposed an interdisciplinary approach called macroecology. This concept has been aided by the advent of phylogeography, for a better knowledge of genetic relationships has had great interdisciplinary value. Two areas of research that should obviously benefit from a macroecological approach are: (1) the question of local vs. regional diversity and (2) the question of whether invader species pose a threat to biodiversity. The two questions are related, because both deal with the vulnerability of ecosystems to penetration by invading species. Biogeographers, who have studied the broad oceanic patterns of dispersal and colonization, tend to regard isolated communities as being open to invasion from areas with greater biodiversity. It became evident that many wide-ranging species were produced in centres of origin, and that the location of communities with respect to such centres had a direct effect on the level of species diversity. Ecologists, in earlier years, thought that a community could become saturated with species and would thereafter be self-sustaining. But recent research has shown that saturation is probably never achieved and that the assembly of communities and their maintenance is more or less dependent on the invasion of species from elsewhere. The study of invasions that take place in coastal areas, usually the result of ship traffic and/or aquaculture imports, has special importance due to numerous opinions expressed by scientists and policy-makers that such invasions are a major threat to biodiversity. However, none of the studies so far conducted has identified the extinction of a single, native marine species due to the influence of an exotic invader. Furthermore, fossil evidence of historical invasions does not indicate that invasive species have caused native extinctions or reductions in biodiversity. Hydrothermal Vent Communities (oceanography) |
