Charles C. Davis

Bio: Charles C. Davis is an academic researcher from Memorial University of Newfoundland. The author has contributed to research in topics: Plankton & Hatching. The author has an hindex of 20, co-authored 64 publications receiving 1237 citations. Previous affiliations of Charles C. Davis include Case Western Reserve University.

Evidence for the eutrophication of lake erie from phytoplankton records

Abstract: The Division Avenue Filtration Plant of the Cleveland Division of Water and Heat has undertaken almost daily phytoplankton counts of water samples from Lake Erie since 1919. Data exist for 25 full years and for 7 additional partial years between 1919 and 1963. There has been a consistent increase in the average quantity of phytoplankton. The vernal and autumnal phytoplankton maxima have consistently become more intense and have lasted longer. The periods of minimun phytoplankton development in winter and summer have become shorter and less well marked, until the winter minimum failed to develop at all in some of the latest years. Certain marked qualitative changes also have occurred. These effects are thought to have been caused by an increasingly rapid eutrophication of the water in Lake Erie.

A study of the hatching process in aquatic invertebrates

Abstract: The hatching process was observed in eggs of Notonecta melaena. A thick outer egg membrane ruptured at the cephalic end by pressure from within, exerted by the expansion of an inner egg membrane which forms a blister over the head. The osmotic nature of this expansion is demonstrated. The pronymph then drank water and its head pushed forward. At the same time, the blister membrane broke. The pronymph then emerged by a combination of a swelling of its body and a worm-like expansion and contraction in the abdominal region. The body swelled from a copious ingestion and absorption of water. The appendages did not participate in any way during hatching. At the termination of the emergence, a second inner membrane was ruptured. Shortly thereafter the pronymph underwent an ecdysis and swam away as a fully formed nymph. The eggs of Ranatra absona hatched in a somewhat similar manner, but the blister membrane was broken only after the head pushed against it. Also, the second inner membrane was ruptured long before the emergence of the nymph had been completed. In addition, there was no pronymphal stage and no ecdysis immediately after emergence. The eggs of Amnicola (?) hydrobioides are described. They were laid at an advanced stage of development. The young were very small (ca. 350 × 270 µ) and were surrounded by single egg membranes whose diameters were about % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaGOmaKaaGm% aaliaabaGaaGymaaqaaiaaikdaaaaaaa!385B!\[2{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern- ulldelimiterspace}\!\lower0.7ex\hbox{$2$}}\] times that of the young. Hatching was through a mechanical tearing motion by the foot and proboscis, but the tearing reflex set in only after the egg membrane collapsed. Evidence is presented which suggests that the collapse was caused by the enzymatic softening of the membrane.

Variations of lorica shape in the genus Ptychocylis (Protozoa: Tintinnina) in relation to species identification

Abstract: A total of 121 photographs was made of specimens in the tintinnid genus Ptychocylis, col- lected in the vicinity of TromsO, northern Norway. Selections are shown from these photographs to il- lustrate variations that occurred. In addition, detailed measurements were undertaken of 165 specimens from the same samples. From all of these and from the literature it is concluded that it is not feasible on the basis of lorica shape to distinguish among the following described species: P. acuta, P. arclica, P. basicurvaia, P. cylindrica. P. drygalskii, P. glatialis and P. obtusa. Further- more, some of the illustrated forms do not correspond to any descriptions found in the literature. It is concluded either that there is one multivariate species encompassing the above list, by priority to be named P. obtusa, or else that other means than the lorica alone must be used to distinguish species in this genus.

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.

Spatial Synchrony in Population Dynamics

Abstract: ▪ Abstract Spatial synchrony refers to coincident changes in the abundance or other time-varying characteristics of geographically disjunct populations. This phenomenon has been documented in the dynamics of species representing a variety of taxa and ecological roles. Synchrony may arise from three primary mechanisms:(a) dispersal among populations, reducing the size of relatively large populations and increasing relatively small ones; (b) congruent dependence of population dynamics on a synchronous exogenous random factor such as temperature or rainfall, a phenomenon known as the “Moran effect”; and (c) trophic interactions with populations of other species that are themselves spatially synchronous or mobile. Identification of the causes of synchrony is often difficult. In addition to intraspecific synchrony, there are many examples of synchrony among populations of different species, the causes of which are similarly complex and difficult to identify. Furthermore, some populations may exhibit complex sp...

Life history patterns in zooplankton

Abstract: Variation in life history patterns has proven amenable to analysis based on the premise that such variation represents adaptive strategies (Cole 1954; Gadgil and Bossert 1970). Highly unpredictable or seasonal environments may favor opportunistic species with high intrinsic rates of increase ("r selected"), while more constant environments do not ("K selected" [MacArthur 1972]). Inspection of a natural community within a single environment reveals that the problem of optimally allocating resources among such conflicting demands as maximizing the potential for rapid increase, predator avoidance, and competitive ability may be met by a virtual continuum of compromises. Zooplankton communities illustrate this well (Hutchinson 1967) and are particularly amenable to quantitative analysis. Parthenogenetic and sexually reproducing zooplankton populations are both well represented in freshwater. Rotifers and cladocerans fall into the former category, have short multivoltine life cycles, are rather unspecialized feeders, and develop large, transitory populations. Other plankters, copepods for example, exhibit longer life cycles and fewer generations to the point of occasionally being biennial or triennial. Quantitative comparisons have not been made, however, beyond the reasonably obvious interpretation that r is likely to be higher in the former cases. This paper attempts to place the comparison of zooplankton life histories on a quantitative basis by estimating intrinsic rates of increase (r), thereby examining alternative life histories which apparently differ in their trade-offs among reproductive potential, predator avoidance, and competitive ability. The implications of this analysis will lend insight into seasonal abundance fluctuations in zooplankton and into certain biogeographic observations, including the composition of freshwater and marine zooplankton communities.

Development and Stability of the Fouling Community at Beaufort, North Carolina

Abstract: Community development was followed for 2 1/2 to 3 1/2 years on unglazed ceramic tile plates (232 cm2), suspended horizontally beneath the Duke University Marine Laboratory dock, in Beaufort, North Carolina. Series of 3 or 4 plates were submerged at approximately the 1st of each month from May—November 1971 and from April—November 1972. Percentage cover for each species that settled and grew on the lower surface was estimated at 6— to 8—week intervals, using 75 points randomly positioned over the plate area. Samples were nondestructive; plates were resubmerged after each census. Larval recruitment was estimated at 1— to 3—week intervals on newly submerged plates. Temperature and salinity were also measured. Initial community development was relatively unpredictable. Larval recruitment patterns varied markedly from year to year and as a result, different patterns of initial community development were observed both within and between years. Instead of preparing the way for subsequent arrivals, most resident adults strongly inhibited the recruitment and growth of other species. Species varied in their ability to resist subsequent invasion as adults and in their ability to invade occupied substrate as larvae. After an unpredictable initial developmental phase, subsequent changes in species composition depended in part on the degree to which larvae were able to invade existing adult assemblages. This in turn depended on the identity of the resident adults and the identity of the invading larvae. As a result, the direction and rate of community development, dependent on the order of initial invasion and subsequent recruitment, were difficult to predict although an equilibrium number of 8—10 species/plate was often observed. Adult residence time was generally <1 year and the mortality and/or disappearance of these adults produced 20—60% free space on an approximately annual basis. This free space was usually occupied by recruits of a different species than the original occupant. The combined addition of species through larval recruitment and subtraction of species as a result of adult mortality produced dramatic changes in community structure each year. There is no reason to believe these changes will ever cease. We conclude that succession in the classical sense (Odum 1969) does not occur in this system because initial development was variable, residents impeded subsequent development instead of enhancing it, and there was no stable climax. There is good reason to believe similar processes occur in other temperate and subtropical fouling communities. We believe these communities are fundamentally different from terrestrial plant communities, where succession may occur, for 3 reasons: (1) the organisms do not alter the substrate they occupy, i.e., “prepare” it for later arrivals, (2) there is no possibility of “storing” dormant “seeds” of successional species. Colonization of free space is generally by animals which have a short—lived, even nonfeeding larvae, (3) most adults are extremely short—lived. An emerging paradigm of marine benthic community organization postulates the existence of competitive hierarchies in which 1 or a few species win in the absence of disturbances. The fouling community appears to lack such dominants.

Nutrients and the productivity of estuarine and coastal marine ecosystems

Abstract: SUMMARY Recent research on estuarine and coastal marine systems has revealed two particularly interesting things about nutrients and productivity. First is the observation that these areas are among the most intensively fertilized environments on earth. Second is the common finding that much of the characteristically high primary productivity of these shallow waters is supported by nutrients released or recycled by pelagic and benthic microheterotrophs. Since nutrient inputs to coastal areas have probably been increasing and are likely to continue to do so, it is particularly important to understand the relationship between nutrient loading and nutrient cycling and the extent to which their interactions may set the levels of primary and secondary production in coastal systems. That some direct relationship exists between the input of nutrients and the productivity of higher trophic levels has been a principle of marine ecology since the turn of the century. It is surprisingly difficult, however, to find q...