The growth and autoecology of two alien invasive species: Sargassum muticum and Undaria pinnatifida spreading in the Venice Lagoon were studied monthly, during one year, in two sites of different ...depth. S. muticum was present year-round and reached its largest size (485 cm) and maximum growth (8.33 cm d−1) at the deepest station. U. pinnatifida was present only from November to May, reaching the highest size (130 cm) in March–April in the shallow station with growth peaks of 2.32 cm d−1. The growth of both species was mainly regulated by water temperature, nutrient concentration, especially nitrogen, and water turbidity. The study highlights the different ecological role already observed for the two species: U. pinnatifida prefers eutrophic areas and is not present along the sea-coastline. Its total standing crop does not exceed 0.2 ktonnes fwt for all the Venice Lagoon. Conversely, S. muticum colonizes areas with a lower eutrophication level, such as the lagoon inlets, reaching a total lagoon standing crop of 4–6 ktonnes fwt.
•Sargassum muticum and Undaria pinnatifida annual growth.•Role of environmental parameters in macroalgal growth.•Annual changes of tissue and environmental nutrient concentrations.•Venice Lagoon.
The introduction and spread of non-indigenous species may have ecological, environmental and economic impacts where they invade. This work aims to study the morphological characteristics, the ...quantitative variables, the possibility of coexistence with other native species and the pathways of introduction of non-indigenous cladoceran Evadne nordmanni (Lovén, 1836) in the middle part of the Caspian Sea. Ballast water is a possible vector for the introduction of cladoceran Evadne nordmanni into the Caspian Sea. The abundance of Evadne nordmanni in all surveyed areas reached an average of 799 individuals/m3. Its biomass was 257.58 mg/m3. Evadne nordmanni significantly contributes to the abundance and biomass of zooplankton in the Middle Caspian Sea. The proportion of the dominant calanoida Acartia tonsa decreased from 71–90% to 40% with the appearance of Evadne nordmanni. Further investigations are needed to analyze the responsible route of Evadne nordmanni introduction to the Caspian Sea and its consequences on biodiversity; since this species is a predator and could have consequences on the feeding conditions of planktivorous fish in the Caspian Sea.
The tropical seagrass
Halophila stipulacea
(Forsskål) Ascherson, 1867 entered in the Mediterranean Sea through the Suez Canal more than 100 years ago. In coastal-marine ecosystems the spatial niche ...of
H. stipulacea
is often overlapped with that of native Mediterranean Sea seagrasses and therefore it might out-compete them. Aiming to better understand its invasiveness potential, we monitored a Southern Mediterranean shallow coastal-marine water habitat from August 2010 to August 2011, where
H. stipulacea
co-occurred with the native seagrass
Cymodocea nodosa
(Ucria) Ascherson, 1870. Besides, the year-round dynamics of
H. stipulacea
was also monitored in four periods. To test the hypothesis that the presence/absence of
H. stipulacea
may have an effect on
C. nodosa
density, we analyzed the shoot density of
C. nodosa
in 8 sites, 4 sites where
H. stipulacea
was present (impacted sites) and 4 where
H. stipulacea
was absent (control sites). The results showed significant differences in
C. nodosa
shoot density according to the presence/absence of
H. stipulacea
, with the lowest values observed in sites where it co-occurred with
H. stipulacea
. We hypothesize that the dense rhizome-sediment net created by
H. stipulacea
can interfere with
C. nodosa
density, pushing down its rhizomes in the anoxic layer. The leaf features of
H. stipulacea
were generally comparable to those of other Mediterranean populations. In January 2011 a significant decline of
H. stipulacea
was observed, maybe related to changes in the environmental conditions that have become unfavorable (e.g. hydrodynamics, turbidity) and, unexpectedly, the seagrass disappeared in April 2011. In January, we also observed the occurrence of the green alien alga
Caulerpa cylindracea
Sonder, 1945 which rapidly invaded the bare substrate left by
H. stipulacea
.
Aquaculture can promote the introduction of non-indigenous species (NIS) into wild marine environments. In addition, NIS aquaculture escapees may hybridize with closely-related native species ...introducing foreign alleles to their gene pool. To quantify the influence of mussel aquaculture on the native community in British Columbia we sampled mussels from fourteen locations on Vancouver Island. There are two native species in this region,
M. trossulus
and
M. californianus
, and two farmed NIS,
Mytilus edulis
and
M
.
galloprovincialis
, both originally from Europe. DNA was extracted from mussel tissue and the mitochondrial cytochrome c oxydase subunit 1 (
COI
) gene was sequenced. One nuclear locus that exhibits different alleles for
M. edulis
,
M. galloprovincialis
and
M. trossulus
(
Glu
-
5′
) was also characterized, using PCR, in order to identify heterozygotes. We found the proportion of NIS introgression depended primarily on farm density. Other habitat traits such as the degree of exposure to the open sea and, to a minor extent, salinity, contributed significantly to explain the distribution of introgressed individuals. Different habitat preference of NIS and native species, and marine currents, provide additional explanations for the distribution of alien and native species along Vancouver Island coasts. As a whole, our results suggest that native
M. trossulus
populations are more introgressed by
M. galloprovincialis
genes in open habitats.
Sabellidae are among the most visible polychaetes of the hard substrate fouling communities and are colonizing new geographic areas. The fouling community was surveyed in 25 shallow coastal estuaries ...on the Atlantic and Pacific coasts of the United States with the specific goal of detecting non-indigenous species. During surveys in 2012 and 2014, specimens of Branchiomma coheni Tovar-Hernández and Knight-Jones, 2006 were found for the first time in Tampa Bay, Florida, occurring at the same marina site (27°53'7.58"N, 82°32'2.29"W) each year and suggesting it is established here. The species was not detected at other sites surveyed in the United States, and has not been reported from the eastern Atlantic or the Mediterranean basin. Type material of B. coheni, specimens from southern Gulf of California, and specimens from the Pacific coast of Mexico, were used to corroborate identification. The transfer of this species by ships via the Panama Canal is a probable mechanism of introduction, based on the current known distribution and shipping traffic patterns. This represents the first record of the species in the Atlantic Ocean. A worldwide update of the records of this species and a list of valid species of the genus Branchiomma with notes on introduced populations are provided, as well as recommendations for accurate identification and sampling.
Most studies of water flea (Crustacea: Cladocera) invasions are concentrated on a few taxa with an obvious harmful influence on native ecosystems, while our knowledge of cases of anthropogenic ...introduction with not-so-obvious consequences, in most other taxa, is poor. We found in the Volga basin (European Russia) a population that contained D. curvirostris Eylmann, 1887 and its hybrids with D. korovchinskyi Kotov et al. 2021. The latter taxon is endemic to the Far East and it has appeared in the Volga basin as a result of past human-mediated transportation. The population from Bakhilovo is represented by two strongly different groups of the COI haplotypes belonging, respectively, to (1) D. curvirostris and (2) D. korovchinskyi. We detected SNPs in the position 60 of the HSP-90ex3 locus and in the 195 positions of 28S rRNA locus, which differentiate two species. Part of the specimens from Bakhilovo belonged to D. curvirostris s.str., demonstrating homozygote SNP sites in two loci, but two specimens had heterozygote SNP sites in both nuclear loci. They belong to D. curvirostris x korovchinskyi hybrids. Most morphological traits of the females were characteristic of D. curvirostris. We found in some specimens some characters which could suggest their hybrid status, but this opinion is a hypothesis only, which needs to be checked on more ample material. The exact hybrid system in this pond is not known. Moreover, we have no evidences of sexual reproduction of the hybrids; they could reproduce by parthenogenesis only as is known for hybrids of the D. pulex group, or continuously crossing with parents like some members of D. longispina group. However, poor parental D. korovchinskyi was not detected in the pond either morphologically or genetically. The exact vector of its past anthropogenic transportation to the Volga is unknown. Most probably, just ephippia of D. korovchinskyi were translocated replaced from the Khabarovsk Territory to the Samara Area somehow. This is the first report on hybrids within the D. curvirostris species complex. Here, we demonstrated that accurate studies with deep resolution increase the number of revealed cryptic invasions. We expect that the number of revealed cases of cryptic interspecific invasions will grow rapidly.
Marine protected areas (MPAs) can protect and restore marine biodiversity and fisheries, but there are concerns that they may also benefit invasive species. The spatial and temporal colonization of ...invasive lionfish (Pterois miles) in the eastern Mediterranean was compared across zones with varying fishing restrictions (no fishing, recreational and commercial fishing, and commercial fishing only), and stations where targeted removal events were conducted by volunteer SCUBA divers. Lionfish density in no fishing areas was nearly double that of areas with commercial fishing only, and over four times greater than in areas where both commercial and recreational fishing were allowed. Lionfish density increased with depth, possibly due to easier human exploitation in shallow waters (0–10 m) that are accessible to recreational spearfishers. Targeted removals by volunteer divers decreased lionfish densities by over 60%, while areas without removals had a 200%–400% increase. Along with management actions, natural and ecological processes might drive lionfish densities within MPAs, and the speed with which lionfish colonized fishery‐restricted zones, emphasized the need for a more sophisticated MPA management strategy that considers invasive species impacts and dynamics in an ecosystem‐based approach.
Invasive lionfish can benefit from the absence of fisheries and thrive within MPAs. Targeted removals and other fishery management measures can be used to suppress their populations and create market opportunities.
Introduction
Both colonial and solitary ascidians (Chordata, Ascidiacea) have been gathering attention due to their impact on coastal environments. The solitary ascidian
Styela plicata
was first ...observed along the coast of Israel in 2014. It is considered a cosmopolitan species of unknown origin, and is well-known for its ability to create large aggregations on artificial substrates in the western Mediterranean Sea, North-Pacific Ocean and the Atlantic. The extreme environmental conditions that characterize the Mediterranean coast of Israel, with a salinity of 40 psu and sea-surface temperature reaching 33°C, may however present a barrier to its future spread.
Methods
We examined the seasonal reproduction patterns and population structure of three populations over two years, in addition to spatial surveys and monitoring oocyte release under laboratory conditions.
Results
Histological sections revealed significant differences in reproduction patterns between seasons and sites, with a higher proportion of the larger oocytes size group observed during the winter for all sites. Along the Israeli coast, with the exception of one site,
S. plicata
is currently restricted to marinas and ports.
Discussion
With an impressive ability to survive the extreme environmental conditions and sustain reproductive populations. Acquiring data on its spread and establishment is essential for modeling
S. plicata’s
distribution under the current and predicted global climate changes, and for developing tools for its mitigation and control.
This paper reviews the available knowledge about faunal xenodiversity in Sicilian inland waters (Italy). The aim is to provide an updated checklist and bibliography of those non-indigenous species ...(NIS) which occur in the island, and to identify possible threats to its native biological diversity. Data were collected through an extensive literature search which encompassed also local journals, books, congress abstracts, and other grey literature. All the collected data were critically revised and, when possible, verified by consulting available collections or through dedicated sampling surveys. Only those data contained in reports indicating precise occurrence localities, which were confirmed by our own observations and\or by at least two independent sources including at least a peer-reviewed publication, were considered as certain. Data in literature that did not meet these criteria were considered doubtful and reported separately as unverified. The information provided by websites has been excluded as it often contains unfounded and\or erroneous data. The fauna of Sicilian inland waters host at present 31 confirmed NIS. In addition, the presence of further 11 taxa is dubious. Among the verified data, invertebrate and vertebrate taxa are nearly equally represented, with 15 and 16 taxa, respectively. With 16 species, the phylum Chordata is by far the most represented, followed by Mollusca (8 species) and Arthropoda (6 species). Most of these species were detected in the last 30 years due to the lack of previous regular studies on Sicilian freshwaters. With few exceptions (e.g., the recent introduction of Xenopus laevis, the African clawed frog), NIS’ effects on native biota have not extensively studied in the island yet. Although the top-down effects caused by introduced vertebrate taxa are known to deeply modify the native structure of the biota, little information is available on the impacts caused by invertebrate taxa, especially the microscopic ones. The presence in Sicily of 11 nonnative species of bony fish is probably the most impacting threat to autochthonous fauna through predation, competition and hybridisation. The results shown in the paper highlight the importance and the urgency of more exhaustive investigations on NIS in Sicilian freshwaters with special regard to less charismatic taxa whose effects on the native biota have never been evaluated yet.
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