scholarly journals Ecological studies on the population dynamics of sea urchins associated with the communities of marine algae

2011 ◽  
Vol 77 (3) ◽  
pp. 352-355
Author(s):  
YUKIO AGATSUMA
Keyword(s):  
Population Dynamics ◽  
Marine Algae ◽  
Sea Urchins ◽  
Ecological Studies

scholarly journals The challenge of managing the commercial harvesting of the sea urchin Paracentrotus lividus: advanced approaches are required

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e10093
Author(s):  
Simone Farina ◽  
Maura Baroli ◽  
Roberto Brundu ◽  
Alessandro Conforti ◽  
Andrea Cucco ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Sea Urchin ◽  
Sea Urchins ◽  
Paracentrotus Lividus ◽  
Current Speed ◽  
Predatory Fish ◽  
Bottom Current ◽  
Environmental Constraints ◽  
Calcareous Rock ◽  
Commercial Size

Sea urchins act as a keystone herbivore in marine coastal ecosystems, regulating macrophyte density, which offers refuge for multiple species. In the Mediterranean Sea, both the sea urchin Paracentrotus lividus and fish preying on it are highly valuable target species for artisanal fisheries. As a consequence of the interactions between fish, sea urchins and macrophyte, fishing leads to trophic disorders with detrimental consequences for biodiversity and fisheries. In Sardinia (Western Mediterranean Sea), regulations for sea urchin harvesting have been in place since the mid 90s. However, given the important ecological role of P. lividus, the single-species fishery management may fail to take into account important ecosystem interactions. Hence, a deeper understanding of population dynamics, their dependance on environmental constraints and multispecies interactions may help to achieve long-term sustainable use of this resource. This work aims to highlight how sea urchin population structure varies spatially in relation to local environmental constraints and species interactions, with implications for their management. The study area (Sinis Peninsula, West Sardinia, Italy) that includes a Marine Reserve was divided into five sectors. These display combinations of the environmental constraints influencing sea urchin population dynamics, namely type of habitat (calcareous rock, granite, basalt, patchy and continuous meadows of Posidonia oceanica), average bottom current speed and predatory fish abundance. Size-frequency distribution of sea urchins under commercial size (<5 cm diameter size) assessed during the period from 2004 to 2007, before the population collapse in 2010, were compared for sectors and types of habitat. Specific correlations between recruits (0–1 cm diameter size) and bottom current speeds and between middle-sized sea urchins (2–5 cm diameter size) and predatory fish abundance were assessed. Parameters representing habitat spatial configuration (patch density, perimeter-to-area ratio, mean patch size, largest patch index, interspersion/juxtaposition index) were calculated and their influence on sea urchin density assessed. The density of sea urchins under commercial size was significantly higher in calcareous rock and was positively and significantly influenced by the density and average size of the rocky habitat patches. Recruits were significantly abundant in rocky habitats, while they were almost absent in P. oceanica meadows. The density of middle-sized sea urchins was more abundant in calcareous rock than in basalt, granite or P. oceanica. High densities of recruits resulted significantly correlated to low values of average bottom current speed, while a negative trend between the abundance of middle-sized sea urchins and predatory fish was found. Our results point out the need to account for the environmental constraints influencing local sea urchin density in fisheries management.

Observations on the ecology and population dynamics of the Blanding's turtle, Emydoidea blandingi

1968 ◽  
Vol 46 (2) ◽  
pp. 288-290 ◽  
Author(s):  
J. Whitfield Gibbons
Keyword(s):  
Population Dynamics ◽  
Reproductive Potential ◽  
Chrysemys Picta ◽  
Painted Turtle ◽  
Seasonal Activity ◽  
Ecological Studies ◽  
Blanding's Turtle ◽  
Reproductive Cycles ◽  
Size And Structure ◽  
Blanding’S Turtle

Ecological studies were made on the Blanding's turtle, Emydoidea blandingi, in southwestern Michigan. Observations were made regarding population size and structure, seasonal activity, and reproductive potential and cycles. Reproductive cycles and periods of terrestrial activity were found to be coincident with those of the painted turtle, Chrysemys picta.

Effects of the parasitic nematode Echinomermella matsi on growth and survival of its host, the sea urchin Strongylocentrotus droebachiensis

1999 ◽  
Vol 77 (1) ◽  
pp. 139-147 ◽  
Author(s):  
Audun Stien
Keyword(s):  
Population Dynamics ◽  
Sea Urchin ◽  
Parasitic Nematode ◽  
Sea Urchins ◽  
Strongylocentrotus Droebachiensis ◽  
Probability Models ◽  
Negative Effects ◽  
Growth And Survival ◽  
Host Growth ◽  
Reproductive Rates

It has been suggested that the parasitic nematode Echinomermella matsi significantly affects the population dynamics of its host, the sea urchin Strongylocentrotus droebachiensis. The effects of infection on both host fecundity and host survival may be of importance. The fecundity of sea urchins is related to their size. Negative effects of infection on host growth will therefore reduce reproductive rates. I estimated the effect of infection on host growth and survival in two naturally infected wild sea urchin populations using a capture-mark-recapture approach. Infected and uninfected sea urchins were captured and marked with unique tags or recaptured seven times from June 1994 to September 1996. The increment in the diameter of marked sea urchins between captures was used to measure sea urchin growth. The effect of E. matsi infection on host growth was small. Mortality rates were estimated using survival probability models based on the methodology developed by Cormack, Jolly, and Seber. The effect of infection on host survival was pronounced, with estimated sea urchin life expectancies reduced by 33-86% by E. matsi infection. This suggests that E. matsi may affect the population dynamics of S. droebachiensis significantly through the effect on host survival.

INDUCED FLUORESCENCE IN GAMETOPHYTES OF SOME LAMINARIALES

1964 ◽  
Vol 42 (9) ◽  
pp. 1173-1181 ◽  
Author(s):  
Kathleen Cole
Keyword(s):  
Fluorescence Microscopy ◽  
Acridine Orange ◽  
Cell Walls ◽  
Marine Algae ◽  
Developmental Stages ◽  
Culture Media ◽  
Ecological Studies ◽  
Calcofluor White ◽  
Fluorescent Compounds

The effectiveness of fluorescence microscopy in cytological studies of some Laminariales in culture has been demonstrated in preliminary experiments. Gametophytes were initiated and grown for several weeks in culture media containing different fluorescent compounds. In addition, culture slides were removed from control dishes at different developmental stages and vitally stained with fluorescent media for periods up to 48 hours. Acridine orange and coriphosphine selectively stained the nuclei and cytoplasm in vivo. However, acridine orange had to be applied in the dark, and applications of both fluors were limited to relatively short staining periods since they were toxic to the cultures after 48 hours. Calcofluor White and Biofluor fluorescent brighteners, particularly Calcofluor White PMS, were highly successful. They were (i) non-toxic to the cultures, (ii) selectively absorbed by the cell walls quickly and permanently, (iii) intensely fluorescent at pH 7.8, (iv) stable, and (v) transported to subsequent gametophytic growth. Actively growing regions of the gametophytes fluoresced most brightly, while reproductive and sporophytic cells absorbed the brighteners very weakly. Possible applications of the brighteners in cytological, genetical, developmental, and ecological studies of the marine algae are suggested.

scholarly journals Multiple Processes Regulate Long-Term Population Dynamics of Sea Urchins on Mediterranean Rocky Reefs

PLoS ONE ◽  
2012 ◽  
Vol 7 (5) ◽  
pp. e36901 ◽  
Author(s):  
Bernat Hereu ◽  
Cristina Linares ◽  
Enric Sala ◽  
Joaquim Garrabou ◽  
Antoni Garcia-Rubies ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Sea Urchins ◽  
Rocky Reefs ◽  
Multiple Processes

scholarly journals The 'Herbivory Uncertainty Principle': application in a cerrado site

2010 ◽  
Vol 70 (2) ◽  
pp. 279-282
Author(s):  
CA Gadotti ◽  
MA Batalha
Keyword(s):  
Population Dynamics ◽  
Plant Community ◽  
Uncertainty Principle ◽  
Human Ecology ◽  
Animal Behaviour ◽  
Ecological Studies ◽  
Visit Frequency ◽  
Whole Plant ◽  
And Control

Researchers may alter the ecology of their studied organisms, even carrying out apparently beneficial activities, as in herbivory studies, when they may alter herbivory damage. We tested whether visit frequency altered herbivory damage, as predicted by the 'Herbivory Uncertainty Principle'. In a cerrado site, we established 80 quadrats, in which we sampled all woody individuals. We used four visit frequencies (high, medium, low, and control), quantifying, at the end of three months, herbivory damage for each species in each treatment. We did not corroborate the 'Herbivory Uncertainty Principle', since visiting frequency did not alter herbivory damage, at least when the whole plant community was taken into account. However, when we analysed each species separately, four out of 11 species presented significant differences in herbivory damage, suggesting that the researcher is not independent of its measurements. The principle could be tested in other ecological studies in which it may occur, such as those on animal behaviour, human ecology, population dynamics, and conservation.

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