scholarly journals Seasonality and trophic diversity in molluscan assemblages from the Bay of Tunis (southern Mediterranean Sea)

2016 ◽  
Vol 17 (3) ◽  
pp. 692 ◽  
Author(s):  
M. ANTIT ◽  
A. DAOULATLI ◽  
J. URRA ◽  
J. L. RUEDA ◽  
S. GOFAS ◽  
...  
Keyword(s):  
Species Richness ◽  
Anthropogenic Impacts ◽  
Seawater Temperature ◽  
Trophic Group ◽  
Indigenous Species ◽  
Soft Bottom ◽  
Trophic Diversity ◽  
Southern Mediterranean ◽  
Evenness Indices ◽  
Non Indigenous Species

Soft bottom molluscan assemblages from the Bay of Tunis have been studied in order to analyse their seasonality and trophic diversity in relation to environmental variables. A total of 147 species of molluscs was identified, with gastropods displaying the highest species richness and bivalves the highest abundances, and including five non-indigenous species such as the dominant ectoparasite Polycerella emertoni. Carnivorous and scavenger gastropods were among the most frequent species, reflecting a diverse benthic community. Seasonal changes were significant, being more acute at 3-4 m than at 10-15 m depth, and were driven mainly by seawater temperature and percentage of organic matter in the sediment. The high affluence of tourists in summer was coincident with high decreases in species richness and abundance of molluscs, together with a strong siltation of the sediment. Nevertheless, most trophic groups remained and the trophic diversity was relatively high. Significant relationships were found between the index of trophic diversity and Shannon-Wiener diversity and evenness indices, suggesting that the identity of the species with its particular trophic trait, together with the good distribution of the individuals among the species (density) would be the drivers for the maintenance of the molluscan food web under environmental stress. The abundance of P. emertoni altered the trophic structure of the molluscan assemblage, with the ectoparasite trophic group reaching an unusual punctual higher dominance. Soft bottom molluscan assemblages of the Bay of Tunis should be taken into account in monitoring programs for anthropogenic impacts and non-indigenous species trends throughout the Mediterranean basin.

scholarly journals Updated checklist of bony fishes along the Libyan coasts (Southern Mediterranean Sea)

2019 ◽  
Author(s):  
HOUSSEIN ELBARAASI ◽  
BAHRIA ELABAR ◽  
SALAMA ELAABIDI ◽  
ASMA BASHIR ◽  
OSAMA ELSILINI ◽  
...  
Keyword(s):  
Small Scale ◽  
Indigenous Species ◽  
Field Surveys ◽  
Complete Representation ◽  
Bony Fishes ◽  
Southern Mediterranean ◽  
The Mediterranean ◽  
Marine Areas ◽  
Non Indigenous Species ◽  
The Mediterranean Basin

 Here we provide an updated review of both native and non-indigenous ichthyofauna occurring in the waters of Libya, one of the largest and less studied marine areas of the Mediterranean basin. With respect to the most recent information, the list of Libyan bony fishes was updated with 104 species for a total of 304 listed taxa. Out of these species, 271 are native, 6 endemic to the Mediterranean, 22 non indigenous of Lessepsian origin and 5 range expanding taxa from Gibraltar. Information on the distribution and abundance of Lessepsian fishes along the Libyan coasts was gained through both field surveys and interviews with local small-scale fishermen, which contributed in filling large information gaps in the area. This combined approach allowed to gather a more complete representation of non indigenous species along the Libyan coasts and indicated three assessment areas, corresponding to the eastern, central and western sectors of the country, which should be considered in future monitoring programs.

Sydney Harbour: a review of anthropogenic impacts on the biodiversity and ecosystem function of one of the world

2015 ◽  
Vol 66 (12) ◽  
pp. 1088 ◽  
Author(s):  
M. Mayer-Pinto ◽  
E. L. Johnston ◽  
P. A. Hutchings ◽  
E. M. Marzinelli ◽  
S. T. Ahyong ◽  
...  
Keyword(s):  
Sustainable Management ◽  
Anthropogenic Impacts ◽  
Habitat Modification ◽  
Indigenous Species ◽  
Benthic Community Structure ◽  
Organic Contamination ◽  
The World ◽  
Sydney Harbour ◽  
Biodiversity And Ecosystem Function ◽  
Non Indigenous Species

Sydney Harbour is a hotspot for diversity. However, as with estuaries worldwide, its diversity and functioning faces increasing threats from urbanisation. This is the first synthesis of threats and impacts in Sydney Harbour. In total 200 studies were reviewed: 109 focussed on contamination, 58 on habitat modification, 11 addressed non-indigenous species (NIS) and eight investigated fisheries. Metal concentrations in sediments and seaweeds are among the highest recorded worldwide and organic contamination can also be high. Contamination is associated with increased abundances of opportunistic species, and changes in benthic community structure. The Harbour is also heavily invaded, but invaders’ ecological and economic impacts are poorly quantified. Communities within Sydney Harbour are significantly affected by extensive physical modification, with artificial structures supporting more NIS and lower diversity than their natural equivalents. We know little about the effects of fishing on the Harbour’s ecology, and although ocean warming along Sydney is among the fastest in the world, we know little about how the ecosystem will respond to warming. The interactive and cumulative effects of stressors on ecosystem functioning and services in the Harbour are largely unknown. Sustainable management of this iconic natural system requires that knowledge gaps are addressed and translated into coherent environmental plans.

Climate change driven massive extirpation of native species from the Israeli Mediterranean shelf

2020 ◽  
Author(s):  
Paolo G. Albano ◽  
Jan Steger ◽  
Marija Bošnjak ◽  
Beata Dunne ◽  
Zara Guifarro ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Native Species ◽  
Large Scale ◽  
Seawater Temperature ◽  
Maximum Size ◽  
Extreme Environment ◽  
Time Range ◽  
Indigenous Species ◽  
Shallow Subtidal ◽  
Non Indigenous Species

<p>We quantify a large-scale extirpation of native species from the Israeli Mediterranean shelf, a region strongly affected by rapidly changing environmental conditions and the introduction of non-indigenous species, based on an extensive sampling programme of mollusks on intertidal to subtidal soft and hard substrata. We reconstruct historical species richness from shelly death assemblages, quantify the time range they cover with radiocarbon dating, and compare their richness with today’s living assemblage diversity. The median native richness is 50% of the historical richness for the intertidal, but only 8% for the subtidal down to 40 m. Samples from the mesophotic zone show a much higher median of 42%, which is likely an underestimation due to sampling constraints. In contrast, non-indigenous species show assemblages matching the historical richness. Seasonality is very strong: autumn samples, after the summer heat peak, are highly impoverished in native species but enriched in non-indigenous ones. Additionally, a comparison between today’s and historical native species maximum size shows that shallow subtidal native populations are mostly non-reproductive. In contrast, non-indigenous species reach reproductive size. These results suggest that a recent large-scale change in environmental conditions is strongly favoring non-indigenous species and is the main cause behind the shallow subtidal native species decline. Such an environmental factor is likely seawater temperature that plays a greater role in the shallow subtidal than in the cooler mesophotic zone, and affects subtidal species more than intertidal ones, pre-adapted to a climatically extreme environment.</p>

scholarly journals Terrestrial ecosystems of the Antarctic Peninsula and their responses to climate change and anthropogenic impacts

2020 ◽  
pp. 84-97
Author(s):  
R. Bargagli ◽  
Keyword(s):  
Antarctic Peninsula ◽  
Native Species ◽  
Environmental Changes ◽  
Anthropogenic Impacts ◽  
Extreme Temperature ◽  
Terrestrial Ecosystems ◽  
Indigenous Species ◽  
Non Indigenous Species ◽  
Food Web Complexity ◽  
The Antarctic

Antarctica and the Southern Ocean are unique natural laboratories where organisms adapted to extreme environmental conditions have evolved in isolation for millions of years. These unique biotic communities on Earth are facing complex climatic and environmental changes. Terrestrial ecosystems in the Antarctic Peninsula Region (APR) have experienced the highest rate of climate warming and, being the most impacted by human activities, are facing the greatest risk of detrimental changes. This review provides an overview of the most recent findings on how biotic communities in terrestrial ecosystems of the Antarctic Peninsula Region (APR) are responding and will likely respond to further environmental changes and direct anthropogenic impacts. Knowledge gained from studies on relatively simple terrestrial ecosystems could be very useful in predicting what may happen in much more complex ecosystems in regions with less extreme temperature changes. The rapid warming of the APR has led to the retreat of glaciers, the loss of snow and permafrost and the increase of ice-free areas, with a consequent enhancement of soil-forming processes, biotic communities, and food web complexity. However, most human activity is concentrated in APR coastal ice-free areas and poses many threats to terrestrial ecosystems such as environmental pollution or disturbances to soilcommunities and wildlife. People who work or visit APR may inadvertently introduce alien organisms and/or spread native species to spatially isolated ice-free areas. The number of introduced non-indigenous species and xenobiotic compounds in the APR is likely to be greater than currently documented, and several biosecurity and monitoring activities are therefore suggested to Antarctic national scientific programs and tourism operators to minimize the risk of irreversible loss of integrity by the unique terrestrial ecosystems of APR.

Non-indigenous marine macroalgae in native communities: a case study in the British Isles

2008 ◽  
Vol 88 (4) ◽  
pp. 693-698 ◽  
Author(s):  
Frederic Mineur ◽  
Mark P. Johnson ◽  
Christine A. Maggs
Keyword(s):  
Species Richness ◽  
Northern Ireland ◽  
Community Composition ◽  
Native Species ◽  
Positive Relationship ◽  
Marine Macroalgae ◽  
Indigenous Species ◽  
Species Introduction ◽  
Southern England ◽  
Non Indigenous Species

It has traditionally been considered that areas with high natural species richness are likely to be more resistant to non-indigenous species than those with lower numbers of species. However, this theory has been the subject of a debate over the last decade, since some studies have shown the opposite trend. In the present study, a macroalgal survey was carried out at 24 localities in Northern Ireland and southern England, using a quadrat approach in the lower littoral. The two opposing hypotheses were tested (negative versus positive relationship between native and non-indigenous species richness) in this marine environment. The effect of the presence of ‘impacts’, potential sources of disturbance and species introduction (e.g. marina, harbour or aquaculture), was also tested. A positive relationship was found between the number of non-indigenous species and the native species richness at the three different scales tested (quadrats, sites and localities). At no scale did a richer native assemblage appear to restrict the establishment of introduced species. The analyses revealed greater species richness and different community composition, as well as more non-indigenous species, in southern England relative to Northern Ireland. The presence of the considered impacts had an effect on the community composition and species richness in southern England but not in Northern Ireland. Such impacts had no effect on the non-indigenous species richness in either area.

scholarly journals Species richness and interacting factors control invasibility of a marine community

2015 ◽  
Vol 282 (1812) ◽  
pp. 20150439 ◽  
Author(s):  
M. L. Marraffini ◽  
J. B. Geller
Keyword(s):  
Species Richness ◽  
Native Species ◽  
Biotic Resistance ◽  
Marine Species ◽  
Indigenous Species ◽  
Total Species Richness ◽  
Species Recruitment ◽  
Non Indigenous Species ◽  
Total Species

Anthropogenic vectors have moved marine species around the world leading to increased invasions and expanded species' ranges. The biotic resistance hypothesis of Elton (in The ecology of invasions by animals and plants , 1958) predicts that more diverse communities should have greater resistance to invasions, but experiments have been equivocal. We hypothesized that species richness interacts with other factors to determine experimental outcomes. We manipulated species richness, species composition (native and introduced) and availability of bare space in invertebrate assemblages in a marina in Monterey, CA. Increased species richness significantly interacted with both initial cover of native species and of all organisms to collectively decrease recruitment. Although native species decreased recruitment, introduced species had a similar effect, and we concluded that biotic resistance is conferred by total species richness. We suggest that contradictory conclusions in previous studies about the role of diversity in regulating invasions reflect uncontrolled variables in those experiments that modified the effect of species richness. Our results suggest that patches of low diversity and abundance may facilitate invasions, and that such patches, once colonized by non-indigenous species, can resist both native and non-indigenous species recruitment.

scholarly journals Juvenile pelagic fish assemblages in the coastal waters of Lebanon: Diversity, biological characteristics & landings

2019 ◽  
Author(s):  
Garabet Kazanjian
Keyword(s):  
Species Richness ◽  
Fish Assemblages ◽  
Niche Partitioning ◽  
Common Species ◽  
Indigenous Species ◽  
Northern Coast ◽  
First Maturity ◽  
Non Indigenous Species ◽  
New Recruits ◽  
Boops Boops

Small pelagic fishes constituted half of the Mediterranean landings and a considerable portion of the Lebanese catches. In this study, the purse seine fishery was analyzed between 2006 and 2007 in two sites along the northern coast of Lebanon.Thirty-six different fish species were collected, out of which seven constituted morethan 97% of the landings. Engraulis encrasicolus, Sardinella aurita and Sardinapilchardus composed 57.7%, 20.9% and 5.6% of the abundance of catches respectively and 31.3%, 19.2%, 9.2% of its biomass. Non-indigenous species comprised 7.2% of the total abundance and 18.7 % of the landing biomass. The fishery targeted mainly the new recruits (0+), and the vast majority of the catches were fishes below their size at first maturity. Diversity and species richness were high in the warmer in the months and low in the colder ones. Temperature and salinity were positively correlated with species richness, while the chlorophyll content of seawater was positively associated with diversity. Clear temporal patterns with distinct shifts of dominance within the landings were detected throughout the year for the most common species. Engraulids dominated catches from October to March, while the rest of the year was characterized by clupeids, Boops boops, and Scomber colias. A temporal niche partitioning seems to exist in the easternmost Mediterranean pelagic waters, possibly to minimize competition.

scholarly journals First records of non-indigenous species in port of Arzew (Algeria: southwestern Mediterranean)

2020 ◽  
Author(s):  
BILEL BENSARI ◽  
LAMIA BAHBAH ◽  
ADLANE LOUNAOUCI ◽  
SEYF EDDINA FAHCI ◽  
ABDERRAHMANE BOUDA ◽  
...  
Keyword(s):  
Hot Spots ◽  
Native Species ◽  
Indigenous Species ◽  
Fishing Vessel ◽  
Fouling Communities ◽  
Southern Mediterranean ◽  
Algerian Coast ◽  
Cryptogenic Species ◽  
Non Indigenous Species ◽  
First Time

Maritime transport is considered to be one of the main factors to transfer non-indigenous species (NIS), through biofouling of ships’ hulls and ballast water. Therefore, ports and marinas constitute hot spots for the introduction of species carried by international shipping and therefore are important sites for initiating biological monitoring. In this study, the port of Arzew (Algeria, Southern Mediterranean) was surveyed for the presence of NIS and cryptogenic species. The fouling communities of floating submerged structures and the hull of a fishing vessel were sampled with a scraper blade. After fixing and separating, the organisms were identified to the lowest possible taxonomic level. The results revealed the presence of 10 NIS and cryptogenic species, including: 1 Ascidiacea, 2 Bryozoa, 3 Crustacea, 1 Mollusca 1 Porifera, and 2 Polychaeta. Five species are reported for the first time from the Algerian coast. This study contributes to the knowledge of non-native species on the Algerian coast and in the Southern Mediterranean and establishes a baseline dataset for future assessments of NIS in ports of Algeria.

The life history and feeding ecology of velvet shell, Velutina velutina (Gastropoda: Velutinidae), a specialist predator of ascidians

2019 ◽  
Vol 97 (12) ◽  
pp. 1164-1176
Author(s):  
P.S. Sargent ◽  
J.-F. Hamel ◽  
A. Mercier
Keyword(s):  
Life History ◽  
Water Temperature ◽  
Feeding Ecology ◽  
Seawater Temperature ◽  
Ecological Knowledge ◽  
Indigenous Species ◽  
Eastern Canada ◽  
Egg Capsules ◽  
Specialist Predator ◽  
Non Indigenous Species

Velvet shell, Velutina velutina (Müller, 1776), is a specialist predator of ascidians, like other members of the gastropod family Velutinidae. Globally, invasive ascidians have become problematic, ecologically and economically, yet ecological knowledge of velutinids remains limited. This study outlines the life history and feeding ecology of V. velutina in eastern Canada based on laboratory work complemented by field observations. The life history of V. velutina is closely linked with ascidians, which serve as prey and protection for their egg capsules. Egg capsules were embedded within tunics of Aplidium glabrum (Verrill, 1871) and Ascidia callosa Stimpson, 1852, with a preference for the latter. Seasonal behavioural shifts were consistent annually and corresponded with seawater temperature cycles. Feeding dominated during the coldest months (January–May), growth occurred as water temperature increased to the annual maximum (June and July), transitioning to mating during the warmest period (July–August), and egg capsule deposition dominated as water temperature declined (November–January). Larvae hatched between January and July after 2–4 months of development. Velutina velutina preyed on all ascidian species presented during this study, including golden star tunicate, Botryllus schlosseri (Pallas, 1766), and vase tunicate, Ciona intestinalis (Linnaeus, 1767), two non-indigenous species, although solitary species were preferred.

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