Gordon Gunter

Bio: Gordon Gunter is an academic researcher from University of Southern Mississippi. The author has contributed to research in topics: Shrimp & Oyster. The author has an hindex of 25, co-authored 107 publications receiving 2093 citations. Previous affiliations of Gordon Gunter include University of Texas at Austin.

Some relations of estuarine organisms to salinity

Abstract: Collectors often ignore salinity while carefully gathering other data with locality records of estuarine organisms, although there has been a great deal of work showing that salinity is a limiting factor to the distribution of many marine organisms, especially as it varies downward, and these limits are often quite sharp. Some recent evidence is reviewed. Hypersalinities are not common in the sea, but where such areas are found on certain coasts, high salinities also limit biotic distributions. The endemic fauna of estuaries is largely sessile. There are a few endemic motile species, chiefly fishes and crustaceans, but the motile fauna is made up mostly of the young of species which spawn offshore in high salinity water and these are sometimes present in vast hordes. Examples are menhaden, mullet, croakers, blue crabs and penaeid shrimp, which all support major fisheries in the United States. Estuaries may be characterized as nursery grounds. They are not refuges for spent races. There are three known types of biological gradients that correspond with salinity gradients. Sessile or only slightly motile marine organisms have optimal salinity ranges for best growth and when the salinities vary away from the optima, either upward or downward, the populations become stunted. A second correlation is between the size of motile organisms and the salinity. In general the smaller and younger ones initially distribute themselves in lower salinity water and migrate towards the sea as they grow larger; thus, the correlation between salinity and size is direct. This correlation is probably dependent upon intrinsic physiological conditions, but more information is needed. The greatest numbers of species of marine plants and animals are found in the photic zone of the shallow sea in full sea water and not in estuaries, as has sometimes been stated. All marine organisms and most estuarine organisms can withstand full sea water, but some of them cannot withstand lowered salinities and thus the species numbers decline with the salinity gradient decline in estuaries. The same thing is noted with the salinity gradient rise in hypersaline areas. The reasons for this situation are not clear, but it shows similarities to the warm to cold decline in numbers of species, away from the tropics, which holds both on land and in the sea. This temperature-species gradient has been explained on the basis that the colder regions of the earth are relatively new and organisms have not yet had time to populate them fully. That explanation is probably not valid, for a parallel situation holds over shorter distances in estuaries, which are not new in terms of the Earth’s history.

Origin of the Tetrapod Limb.

Abstract: The paired fins of fishes were first used as props and supports for resting on the bottom; these were later used in a clumsy, walking manner, and this behavior perforce began first in the water, because the weak props could not support the animals without the water bouyancy; increased perfection of the mechanics of walking took place in the shallows; which was a refuge from the chief predators; the land was also attractive as a haven and as a source of food; the first vertebrate invaders of land probably had fins, and these became legs by enlargement of the fin base and loss of fin rays; these original limbs and girdles were weak and probably underwent a considerable period of evolution in swampy country; later they were perfected by further selection when it became necessary for early amphibians to move across dry land because of a failing local water supply. This syllogism conforms to the known behavior and capabilities of fishes and amphibians and to the general facts of zoology and paleontology. It suggests that common, continuous activities and stresses—escape from enemies and food getting—led to the origin of the tetrapod limb. This obviates the necessity for explaining how discontinuous and somewhat catastrophic events, such as the drying up of water bodies, could have led to the origin of limbs, which at the very outset had to be fairly strong. The general theory stated here is fairly clearly implied by Berry (8), who said, "Those fishy pioneers with air-bladders —and paired fins—which, after ages of using their fins for pushing and paddling themselves over mud flats, gradually ventured onto drier and drier ground—where they avoided the competition for food—and the dangers of swarming hordes of ganoid pirates of the waters, were the ancestors of the amphibians."

Supporting Online Material for Spreading Dead Zones and Consequences for Marine Ecosystems

Abstract: Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels. Enhanced primary production results in an accumulation of particulate organic matter, which encourages microbial activity and the consumption of dissolved oxygen in bottom waters. Dead zones have now been reported from more than 400 systems, affecting a total area of more than 245,000 square kilometers, and are probably a key stressor on marine ecosystems.

Classification of Wetlands and Deepwater Habitats of the United States

Abstract: From foreword: "This report represents the most current methodology available for wetland classification and culminates a long-term effort involving many wetland scientists."

The Identification, Conservation, and Management of Estuarine and Marine Nurseries for Fish and Invertebrates

Abstract: Michael W. Beck, Kenneth L. Heck, Jr., Kenneth W. Able, Daniel L. Childers, David B. Eggleston, Bronwyn M. Gillanders, Benjamin Halpern, Cynthia G. Hays, Kaho Hoshino, Thomas J. Minello, Robert J. Orth, Peter F. Sheridan and Michael P. Weinstein

The Effects of Harmful Algal Blooms on Aquatic Organisms

Abstract: (2002). The Effects of Harmful Algal Blooms on Aquatic Organisms. Reviews in Fisheries Science: Vol. 10, No. 2, pp. 113-390.

Temperature Tolerances of North American Freshwater Fishes Exposed to Dynamic Changes in Temperature

Abstract: Traditionally lower and upper temperature tolerances of fishes have been quantified in the laboratory via three different experimental approaches: the Fry or incipient lethal temperature (ILT), critical thermal (CTM) and chronic lethal (CLM) methodologies. Although these three experimental laboratory approaches generate endpoints which are quantitatively expressed as a temperature, are determined experimentally with random samples of fish acclimated to specific temperatures, and involve both time and temperature as major test variables, they do not quantify the same response. All three approaches generate valuable, albeit different, information concerning the temperature tolerance of a species. In this review we have summarized published research concerning the tolerance of North American freshwater fishes to dynamic changes in temperature, i.e., tolerance is tested by methods that gradually change temperatures until biological stress is observed. We found more than 450 individual temperature tolerances listed in 80 publications which present original dynamic temperature tolerance data for 116 species, 7 subspecies and 7 hybrids from 19 families of North American freshwater fishes. This total represents about 1/3 of the families and 1/6 of the known North American freshwater species. Temperature tolerance data were partitioned by experimental approach, i.e., critical thermal method (CTM) and chronic lethal method (CLM), and direction of temperature change. Although both CTM and CLM expose fish to dynamic changes in water temperature, these two methods differ in temperature change rates and test endpoints, and hence measure different aspects of thermal stress. A majority of the 80 studies employed CTM to assess temperature tolerance, in particular determination of CTmaxima. One or more CTmaxima has been reported for 108 fishes. Twenty-two fishes have reported highest CTmaxima of 40°C or higher. Several species in the family Cyprinodontidae have generated some of the highest CTmaxima reported for any ectothermic vertebrate. For a variety of reasons, data concerning tolerance of low temperatures are less plentiful. Low temperature tolerance quantified as either CTminima or CLminima were found for a total of 37 fishes. Acclimation temperature exerts a major effect on the temperature tolerance of most North American fish species and it is usually strongly linearly related to both CTmaxima and CTminima. Although we uncovered dynamic temperature tolerance data for 130 fishes, only a single dynamic, temperature tolerance polygon has been published, that for the sheepshead minnow, Cyprinodon variegatus.