scholarly journals Size-frequency distribution of coral assemblages in insular shallow reefs of the Mexican Caribbean using underwater photogrammetry

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e8957 ◽  
Author(s):  
Roberto C. Hernández-Landa ◽  
Erick Barrera-Falcon ◽  
Rodolfo Rioja-Nieto
Keyword(s):  
Species Richness ◽  
Frequency Distribution ◽  
Dominant Species ◽  
Coral Cover ◽  
Sampling Area ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Frequency ◽  
Reef Health ◽  
Minimum Sampling Area

The characterisation of changes in coral communities depends heavily on systematic monitoring programs and the collection of necessary metrics to assess reef health. Coral cover is the most used metric to determine reef health. The current organizational shift in coral requires the evaluation of complementary metrics, such as colony size and frequency distributions, which help to infer the responses of the coral populations to local stress or larger scale environmental changes. In this study, underwater digital photogrammetry techniques were used to assess the live cover of all coral colonies ≥3 cm2 and determine the size-frequency distribution of the dominant species in the shallow reefs of the Cozumel Reefs National Park (CRNP). In addition, the minimum sampling area (m2) needed to obtain a representative sample of the local species pool was estimated. Areas between 550 and 825 m2 per reef were photographed to generate high-resolution digital ortho-mosaics. The live area of the colonies was digitised to generate community matrices of species and abundance. EstimateS software was used to generate accumulation curves and diversity (Shannon H′) at increasing area intervals. Chi-Square tests (χ2, p = 0.05) were used to compare the observed vs estimated species richness. Spearman’s coefficients (rs), were calculated to correlate the increase in sampling area (m2) vs H′, and the Clench’s function was used to validate the observed richness (R2 = 1 and R > 90%). SIMPER analysis was performed to identify dominant species. Comparisons in terms of abundance, coral cover and size-frequencies were performed with Kruskal-Wallis (H test, p = 0.05), and paired Mann-Whitney (U test, p = 0.05). In order to obtain 90% of the species richness, a minimum sampling area of 374 m2is needed. This sampling area could be used in shallow Caribbean reefs with similar characteristics. Twelve (mainly non-massive) species: Agaricia agaricites, A humilis, A. tenuifolia, Eusmilia fastigiata, Meandrina meandrites, Montastrea cavernosa, Orbicella annularis, Porites astreoides, P. porites, Pseudodiploria strigosa, Siderastrea radians andS. siderea, were dominant in terms of abundance and coral cover. A significant increase (p < 0.05) in the number of colonies and live coral (m2) was observed from north to south of the study area. Furthermore, a wide intraspecific variation of size-frequency, even between adjacent reefs, was also observed. The size-frequency distributions presented positive skewness and negative kurtosis, which are related to stable populations, with a greater number of young colonies and a constant input of recruits. Considering the increase in disturbances in the Caribbean and the appearance of a new coral disease, digital photogrammetry techniques allow coral community characteristics to be assessed at high spatial resolutions and over large scales, which would be complementary to conventional monitoring programs.

scholarly journals 2.2.2 The Size Frequency Distribution and Rate of Production of Microcraters

1976 ◽  
Vol 31 ◽  
pp. 227-231
Author(s):  
D. A. Morrison ◽  
E. Zinner
Keyword(s):  
Frequency Distribution ◽  
Lunar Surface ◽  
Particle Flux ◽  
Surface Orientation ◽  
Submicron Particle ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Crater Size ◽  
Size Frequency ◽  
Micron Diameter

AbstractCrater size frequency distributions vary to a degree which probably cannot be explained by variations in lunar surface orientation of the crater detectors or changes in micrometeoroid flux. Questions of sample representativity suggest that high ratios of small to large craters of micrometeoroids (e.g., a million 1.0 micron craters for each 500 micron crater) should be the most reliable. We obtain a flux for particles producing 0.1 micron diameter craters of approximately 300 per cm2 per steradian per year. We observe no anisotropy in the submicron particle flux between the plane of the ecliptic and the normal in the direction of lunar north. No change in flux over a 106 year period is indicated by our data.

scholarly journals Testing size–frequency distributions as a method of ontogenetic aging: a life-history assessment of hadrosaurid dinosaurs from the Dinosaur Park Formation of Alberta, Canada, with implications for hadrosaurid paleoecology

Paleobiology ◽  
2020 ◽  
Vol 46 (3) ◽  
pp. 379-404
Author(s):  
Mateusz Wosik ◽  
Kentaro Chiba ◽  
François Therrien ◽  
David C. Evans
Keyword(s):  
Life History ◽  
Body Size ◽  
Frequency Distribution ◽  
Growth Rates ◽  
Long Bone ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Frequency ◽  
Combining Data ◽  
Dinosaur Park Formation

AbstractHadrosaurid dinosaurs, the dominant large-bodied terrestrial herbivores in most Laurasian Late Cretaceous ecosystems, have an exceptional fossil record consisting of many species known from partial ontogenetic series, making them an ideal clade with which to conduct life-history studies. Previous research considered the Dinosaur Park Formation (DPF) of Alberta as an attritional, or time-averaged, sample and interpreted size–frequency distribution of long bones collected from the DPF with three size classes to suggest that hadrosaurids from the DPF attained near-asymptotic body size in under 3 years. This conflicted with previously published osteohistological estimates of 6+ years for penecontemporaneous hadrosaurids from the Two Medicine Formation (TMF) of Montana, suggesting either extreme variation in hadrosaurid growth rates or that size–frequency distributions and/or osteohistology and growth modeling inaccurately estimate ontogenetic age.We tested the validity of the previously proposed size–age relationship of hadrosaurids from the DPF by significantly increasing sample size and combining data from size–frequency distributions and osteohistology across multiple long-bone elements. The newly constructed size–frequency distributions typically reveal four relatively distinct size–frequency peaks that, when integrated with the osteohistological data, aligned with growth marks. The yearling size class was heavily underrepresented in the size–frequency distribution. If not due to preservation, this suggests that either juvenile (<2 years of age) hadrosaurids from the DPF had increased survivorship following an initially high nestling mortality rate or that yearlings were segregated from adults. A growth-curve analysis revealed asymptotic body size was attained in approximately 7 years, which is consistent with hadrosaurids from the TMF. The data suggest size–frequency distributions of attritional samples underestimate age and overestimate growth rates, but when paired with osteohistology can provide unique life-history insights.

scholarly journals SMALL CRATERS AND THEIR DIAGNOSTIC POTENTIAL

2017 ◽  
Vol XLII-3/W1 ◽  
pp. 23-27
Author(s):  
R. Bugiolacchi
Keyword(s):  
Power Function ◽  
Frequency Distribution ◽  
Central Area ◽  
Saturation Level ◽  
The Moon ◽  
Current Estimate ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Frequency ◽  
Diagnostic Potential

I analysed and compared the size-frequency distributions of craters in the Apollo 17 landing region, comprising of six mare terrains with varying morphologies and cratering characteristics, along with three other regions allegedly affected by the same secondary event (Tycho secondary surge). I propose that for the smaller crater sizes (in this work 9&amp;ndash;30&amp;thinsp;m), a] an exponential curve of power &amp;minus;0.18D can approximate Nkm<sup>&amp;minus;2</sup> crater densities in a regime of equilibrium, while b] a power function D<sup>&amp;minus;3</sup> closely describes the factorised representation of craters by size (1&amp;thinsp;m). The saturation level within the Central Area suggests that c] either the modelled rates of crater erosion on the Moon should be revised, or that the Tycho event occurred much earlier in time than the current estimate. We propose that d] the size-frequency distribution of small secondary craters may bear the signature (in terms of size-frequency distribution of debris/surge) of the source impact and that this observation should be tested further.

scholarly journals Variation in the distribution of Corbicula species (Mollusca: Bivalvia: Corbiculidae) after 25 years of its introduction in the Río de la Plata, Argentina

2017 ◽  
Vol 34 ◽  
pp. 1-6 ◽  
Author(s):  
Yamila Reshaid ◽  
Luciana Cao ◽  
Francisco Brea ◽  
María Ortiz Blanche ◽  
Santiago Torres ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Buenos Aires ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
La Plata ◽  
Size Frequency ◽  
Population Structures

In 1981, Corbiculafluminea (Müller, 1774) and C.largillierti (Philippi, 1844) were recorded at the Río de la Plata River. During the 1980’s, C.largillierti was found on a continuous fringe in the shore of that river, while C.fluminea was only found North of Buenos Aires’ harbor. Ten years later, C.fluminea spread to Punta Indio, while C.largillierti remained restricted to tributary streams. The density and size frequency distribution of both species were compared with previous data from samples performed in the same area in 1985–1989. The aim of this research was to determine whether the densities of both species decreased; whether C.fluminea is still more abundant than C.largillierti; and whether the size frequency distributions indicate different population structures from those observed in the end of the 1980’s. Nine localities from the river shore were sampled, and each individual was identified and measured. The size of C.fluminea varied between 2 and 39 mm, showing the highest frequency of individuals between 20 and 25 mm; furthermore the density decreased 90% in 2015/2016. No specimens of C.largillierti were found. In conclusion, the populations of Corbicula inhabiting the Río de la Plata River are retracting.

scholarly journals Catchability of the southern rock lobster Jasus edwardsii. II. Effects of size

2002 ◽  
Vol 53 (8) ◽  
pp. 1149 ◽  
Author(s):  
P. E. Ziegler ◽  
C. R. Johnson ◽  
S. D. Frusher ◽  
C. Gardner
Keyword(s):  
Frequency Distribution ◽  
Rock Lobster ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Size Classes ◽  
Size Frequency ◽  
Jasus Edwardsii ◽  
Behavioural Interactions ◽  
Males And Females ◽  
Relative Selectivity

For most of the year, the size-frequency distribution of trap-caught southern rock lobster, Jasus edwardsii, reflected size-specific catchability rather than the size-frequency distribution of the population in a scientific reserve in Tasmania, Australia. The size-frequency distributions of the population on the ground and of lobsters captured in traps were similar only during a few months, typically during moulting and mating. Small males and females were usually under-represented in traps. Catchability generally increased with size, but varied with sex and season. During moulting and mating, size-specific catchability and relative selectivity of larger animals were similar to or lower than for smaller animals. The relative pattern of catchability throughout the year was similar for most size classes within each sex. Negative associations between small and large lobsters in traps were stronger in winter than in summer, indicating strong behavioural interactions. These interactions could explain the lower catchability of smaller lobsters. Relative selectivity estimates using tag–recapture and size-specific catchability data provided generally similar results.

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

2011 ◽  
Vol 4 (2) ◽  
pp. 163-169 ◽  
Author(s):  
Ritwik Dasgupta
Keyword(s):  
Frequency Distribution ◽  
Primary Productivity ◽  
Egg Size ◽  
Zooplankton Abundance ◽  
Trophic Conditions ◽  
Size Frequency Distribution ◽  
Size Frequency ◽  
High Predation ◽  
Hatchling Size ◽  
Predation Rates

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

SIZE FREQUENCY DISTRIBUTION BIASES IN HORSESHOE CRAB MOLT ASSEMBLAGES: IMPLICATIONS FOR THE FOSSIL RECORD

2016 ◽  
Author(s):  
Shelly J. Wernette ◽  
◽  
Scott Evans ◽  
Christine Hall ◽  
Mary L. Droser ◽  
...  
Keyword(s):  
Frequency Distribution ◽  
Fossil Record ◽  
Horseshoe Crab ◽  
Size Frequency Distribution ◽  
Size Frequency

scholarly journals Linking population size structure, heat stress and bleaching responses in a subtropical endemic coral

Coral Reefs ◽  
2021 ◽  
Author(s):  
Liam Lachs ◽  
Brigitte Sommer ◽  
James Cant ◽  
Jessica M. Hodge ◽  
Hamish A. Malcolm ◽  
...  
Keyword(s):  
Heat Stress ◽  
Size Structure ◽  
Temporal Trends ◽  
Early Recovery ◽  
Size Frequency Distribution ◽  
Frequency Distributions ◽  
Community Organisation ◽  
Size Frequency ◽  
Eastern Australia

AbstractAnthropocene coral reefs are faced with increasingly severe marine heatwaves and mass coral bleaching mortality events. The ensuing demographic changes to coral assemblages can have long-term impacts on reef community organisation. Thus, understanding the dynamics of subtropical scleractinian coral populations is essential to predict their recovery or extinction post-disturbance. Here we present a 10-yr demographic assessment of a subtropical endemic coral, Pocillopora aliciae (Schmidt-Roach et al. in Zootaxa 3626:576–582, 2013) from the Solitary Islands Marine Park, eastern Australia, paired with long-term temperature records. These coral populations are regularly affected by storms, undergo seasonal thermal variability, and are increasingly impacted by severe marine heatwaves. We examined the demographic processes governing the persistence of these populations using inference from size-frequency distributions based on log-transformed planar area measurements of 7196 coral colonies. Specifically, the size-frequency distribution mean, coefficient of variation, skewness, kurtosis, and coral density were applied to describe population dynamics. Generalised Linear Mixed Effects Models were used to determine temporal trends and test demographic responses to heat stress. Temporal variation in size-frequency distributions revealed various population processes, from recruitment pulses and cohort growth, to bleaching impacts and temperature dependencies. Sporadic recruitment pulses likely support population persistence, illustrated in 2010 by strong positively skewed size-frequency distributions and the highest density of juvenile corals measured during the study. Increasing mean colony size over the following 6 yr indicates further cohort growth of these recruits. Severe heat stress in 2016 resulted in mass bleaching mortality and a 51% decline in coral density. Moderate heat stress in the following years was associated with suppressed P. aliciae recruitment and a lack of early recovery, marked by an exponential decrease of juvenile density (i.e. recruitment) with increasing heat stress. Here, population reliance on sporadic recruitment and susceptibility to heat stress underpin the vulnerability of subtropical coral assemblages to climate change.

scholarly journals Blocks Size Frequency Distribution in the Enceladus Tiger Stripes Area: Implications on Their Formative Processes

Universe ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 82
Author(s):  
Maurizio Pajola ◽  
Alice Lucchetti ◽  
Lara Senter ◽  
Gabriele Cremonese
Keyword(s):  
Frequency Distribution ◽  
Power Law ◽  
Size Frequency Distribution ◽  
Surface Stresses ◽  
Size Frequency ◽  
The One ◽  
Power Law Index ◽  
Comet 67P ◽  
South Polar ◽  
Degree Of Fragmentation

We study the size frequency distribution of the blocks located in the deeply fractured, geologically active Enceladus South Polar Terrain with the aim to suggest their formative mechanisms. Through the Cassini ISS images, we identify ~17,000 blocks with sizes ranging from ~25 m to 366 m, and located at different distances from the Damascus, Baghdad and Cairo Sulci. On all counts and for both Damascus and Baghdad cases, the power-law fitting curve has an index that is similar to the one obtained on the deeply fractured, actively sublimating Hathor cliff on comet 67P/Churyumov-Gerasimenko, where several non-dislodged blocks are observed. This suggests that as for 67P, sublimation and surface stresses favor similar fractures development in the Enceladus icy matrix, hence resulting in comparable block disaggregation. A steeper power-law index for Cairo counts may suggest a higher degree of fragmentation, which could be the result of localized, stronger tectonic disruption of lithospheric ice. Eventually, we show that the smallest blocks identified are located from tens of m to 20–25 km from the Sulci fissures, while the largest blocks are found closer to the tiger stripes. This result supports the ejection hypothesis mechanism as the possible source of blocks.

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