Marine Biology Leviton Pdf Download
the true number of nis that make their way to a new ecosystem is, as yet, unknown. environmental dna (edna) technologies are now beginning to provide a useful tool to improve our ability to detect and monitor the actual number of nis. edna methods involve extracting dna from organisms and then detecting it in the environment, either directly or indirectly using specific primers and polymerase chain reaction (pcr) technologies (see  for a review). however, the study of edna has been limited by (i) dna extraction efficiency, (ii) dna extraction method, (iii) pcr methodology and (iv) the lack of edna database resources. to date, most of the data are from marine fish and aquatic insects. we will briefly describe the state of the art of edna in marine nis detection and monitoring before concluding with an outlook on future research directions.
historically, attempts to detect and monitor marine nis using genetic markers have been limited by the difficulty of obtaining sufficient genetic material and standardization of dna extraction and pcr methodology. while the dna of some marine nis has been successfully amplified from water samples using a polymerase chain reaction (pcr) approach, this is not universal. for example, some marine nis have been detected using edna but only some of the genetic markers present in the dna sequence from the species have been amplified (e.g., ). furthermore, some edna methods may not be sensitive enough to detect very low levels of organisms in the environment, because dna of some marine nis is highly fragmented (e., ). as a consequence, the dna sequence of some marine nis may not be present in the edna database and therefore may be overlooked [ 42 ]. furthermore, edna technologies have been primarily used to estimate the abundance of a species, rather than to assess its presence. regardless of the technologies used, edna is still an indirect method of detection, which is not ideal for nis detection in new environments.
invasive alien species have been introduced into the marine environment in an increasing number of locations, and the introduction of new species has been linked with changes in the structure of marine communities. invasive alien species can have a positive effect on the environment, and some may even have economic value. however, most alien species are harmful to the environment, and some have a negative effect on human health. many studies have focused on the effects of temperature on many aspects of the biology of marine organisms, including physiology, growth, development, reproduction, and mortality [ 12 ]. for example, lower growth rates in larval corals have been associated with increased temperature [ 13, 14 ], while mortality of young coral larvae has also been observed [ 15 ]. reproductive success is also strongly associated with temperature. in a study of the caribbean sea, it was found that coral larvae success and survivorship increased with increasing temperatures in the first two weeks post-hatching, but declined with increasing temperatures during the third week [ 16 ]. similarly, it was demonstrated that coral larvae reach sexual maturity at higher temperatures in the caribbean sea, and that coral and coral-associated fauna have lower rates of reproduction at lower temperatures [ 17 ]. temperature also affects the physiology of the alga amphiroa fragilissima. higher temperature has been shown to decrease photosynthetic capacity in this species, as well as to increase carbon allocation to reproduction, growth, and respiration [ 18 ]. also, temperature can affect the water chemistry. for example, the tolerance of amphiroa fragilissima to a range of inorganic constituents (e.g., calcium, magnesium, potassium, and sodium) was higher at higher temperatures, and a similar response was reported for coral [ 19 ]. temperature can also affect the distribution of coral species. for example, it was found that coral species distributed in the mediterranean sea are mainly present at low latitudes, and most species in the red sea are distributed between 10° and 30° latitude [ 20 ]. increasing temperatures can also affect the distribution of many nis. for example, a shift in the temperature optimum of the ciliate bittium reticulatum was found to cause a shift in the distribution of this species, and possibly has influenced the introduction of this species into the atlantic [ 21 ]. 5ec8ef588b