Advances in Oceanography and Limnology
ISSN / EISSN : 1947-5721 / 1947-573X
Published by: PAGEPress Publications (10.4081)
Total articles ≅ 193
Latest articles in this journal
Advances in Oceanography and Limnology, Volume 12; https://doi.org/10.4081/aiol.2021.9811
The design and establishment of Marine Ecological Observatories (MEOs) are fostered at the European level. MEOs should adopt a holistic view, integrating and harmonizing long-term oceanographic and ecological research and monitoring, and increasing conservation strategies effectiveness according to the ecological connectivity concept. The data and knowledge collected and made available through MEOs should inform policies dealing with conservation and management of the marine environment. We present and discuss these issues in the Adriatic Sea context, where the transnational ecological observatory “ECOAdS” is under development in the framework of the Interreg Italy-Croatia project ECOSS (Observing System in the Adriatic Sea: oceanographic observations for biodiversity), which aims to support Natura 2000 network implementation and cross-border coordination of multiple monitoring initiatives. We analyse the main EU directives that deal with marine conservation, notably the Habitats and Birds directives, the Water Framework Directive, and the Marine Strategy Framework Directive, as they are the primary instruments that can guide the development of the observatory while strengthening cooperation at the basin scale. We bring out the synergies and discrepancies among these legal instruments, and build on them ECOAdS as a monitoring platform that may respond and contribute to their requirements, boosting the synergies and overcoming the weaknesses. Finally, we provide some hints for the further development of this transnational MEO as a collector of the existing monitoring efforts aimed at harmonizing their approaches and incorporating the ecological connectivity to foster an ecosystem-based approach to conservation management.
Advances in Oceanography and Limnology, Volume 12; https://doi.org/10.4081/aiol.2021.9704
To understand the spatial and temporal variations in the extent and timing of sea ice in the Caspian Sea (CS), 15 years of sea ice presence and its phenology (freeze-up, break-up, and duration) were studied in the Northern CS (NCS) for a period from 2004 to 2018. This study indicated that the percentage of sea ice covered area in the CS showed fluctuations ranging from 54.2% in 2004 to more than 89% in 2006 and 2008. This study, furthermore, found regional differences within the NCS in sea ice phonological features during 2004 to 2018. Specifically, earlier sea ice formation, later ice melt, and longer ice periods were observed in the eastern than the western NCS. Noticeable interannual changes were also observed in the timing and duration of the NCS ice (2004-2018). However, most parts of the NCS did not show significant trends (P>0.05) in the formation, decay, and duration of sea ice and their interannual variability. The observed spatial and temporal patterns in the CS ice can have implications for phytoplankton blooms and higher trophic levels, such as fish and endangered Caspian seal populations and merits further investigation.
Advances in Oceanography and Limnology, Volume 12; https://doi.org/10.4081/aiol.2021.9119
Periphytic diatoms growing on aquatic turtle carapaces provide an interesting example of biofouling on an animal substrate. This study dealt with the question of the specificity of epizoic diatom communities for the case of the European pond turtle (Emys orbicularis) and across five water bodies in South-Eastern France. 375 diatom taxa have been identified on the European pond turtle carapace. The results showed that the epizoic communities of the five sites were significantly different from each other. The epizoic diatom communities could be clearly distinguished from epilithic and epiphytic communities only in two out of five sites. The differences in composition at the two sites resulted from the greater abundance of some species and life forms. However, the characteristic pattern of diatom communities on the carapaces was not the same at the two sites. It therefore appeared that the European pond turtle’s carapace did not harbour specific diatom communities and can rather be considered a neutral substrate.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.9500
The freshwater genus Unruhdinium includes dinoflagellates hosting a tertiary diatom endosymbiont. Some of the species belonging to this genus form high-biomass blooms. In this study, data on the ecology, morphology and molecular identity of Unruhdinium penardii were reported for the first time from a Mediterranean reservoir (Cedrino Lake, Sardinia, Italy). The ecology of the species and its bloom events were examined along a multiannual series of data (2010-2017). Cell morphology was investigated using field samples and six cultures established by cell isolation. A molecular identification of the six strains was performed. Wild and cultured cells shared the same morphology, showing a prominent apical pore complex and two/three more or less prominent hypothecal spines as distinctive characters in light microscopy. Molecularly, the six cultured strains corresponded to the same taxonomic entity with sequences only differing in a few polymorphic positions for the studied markers SSU rDNA, LSU rDNA, ITS and endosymbiont SSU rDNA. All markers showed 99.5%−100% similarity with the available U. penardii sequences. Seasonality of U. penardii revealed its preference for the colder semester (from December to June) with bloom events restricted to late winter/early spring months. Three blooms resulting in reddish water discolorations were observed along the study period (2011, 2012 and 2017). GLMs revealed a significant role of water depth, temperature, and reactive phosphorous in determining the highest cell densities (>5 x 104 cells L-1). The results obtained contribute to the increase of field ecology knowledge on this species, demonstrating it is well established in the Mediterranean area, and being able to produce recurrent high biomass blooms in the studied reservoir.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.9471
Mediterranean giant red shrimp Aristaeomorpha foliacea (Risso, 1827) is one of the dominant species in deep-sea megafaunal assemblages, plays a key role in deep-sea communities and it is considered one of the most important targets of deep-water trawl fishing. Although a large number of studies have analysed the spatial distribution of epibenthic crustaceans in bathyal habitats with respect to environmental, geomorphological and hydrological factors, as well as fishing pressure, the manner in which these variables synergistically affect the spatio-temporal changes of giant red shrimp is unclear. To analyse the possible effects of abiotic predictors on the spatio-temporal distribution of giant red shrimp, Generalized Additived Models (GAMs) and Regression Trees were produced. Biological data were collected during the MEDITS trawl surveys carried out in the Sea of Sardinia (2009-2014), during which environmental data were obtained with a multiparametric probe. A longitudinal (west-east) trend was found, with higher abundances at depths of 400-600 m, corresponding to salinity values of 38.1-38.5 psu and temperatures of 13.6-13.8°C. Our results confirm the existence of a tight linkage between the distribution of the Levantine Intermediate Water (LIW) from the eastern Mediterranean Sea and the preferential habitat characteristics of the giant red shrimp. We suggest that a deeper knowledge of the relationships between abiotic (hydrological) factors in the water column and the distribution of Mediterranean resources, such as the giant red shrimp, can provide valuable support for their better management, at the local scale (Sardinia) and across the whole Mediterranean Sea.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.9508
Based on the last decade of activities at the Italian Long Term Ecological Research network (LTER-Italy), I describe and highlight here some major outcomes and challenges, by picturing different voices, which we are listening to and we are talking with. Organisms, ecosystems, methodologies, data, researchers, stakeholders and citizens: their “voices” - which we receive, interpret and express - create our experience and knowledge, which we share with and convey to our contemporaries and future generations. One of the main narrator’s voices will be that of plankton: how we “listen” to them, describe and share long-term data and researches, also with the wide public. Through the “voices from the water” I will report and discuss experiences, which have been relevant also to open up the views on the role that science is challenged to play in a world of rapid change, characterized by complexity and contradictions. In particular I will consider: (i) the voices coming from various LTER aquatic sites, mainly addressing the comparison among them, (ii) how to make the voices most harmonized and audible through the open science approach, and (iii) how to put the LTER voices in an effective dialogue with society. Finally I will share some thoughts about the necessity and the possibility to open the purely scientific cognitive approach to other forms of knowledge.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.8781
River ecosystems are characterised by a naturally high level of hydrodynamic perturbations which create aquatic-terrestrial habitats indispensable for many species, as well as for the human beings' welfare. Environmental degradation and habitat loss caused by increasing anthropogenic pressures and global change affect freshwater aquatic ecosystems worldwide and have caused changes in water flow regimes and channels morphologies. These, in turn, decreased the natural flow capacity and reduced habitat availability, thus causing severe degradation of rivers' ecological integrity. The ecological flow (e-flow) is commonly intended as the quantity, timing, duration, frequency and quality of water flows required to sustain freshwater, estuarine and near‐shore ecosystems and the human livelihoods and well‐being. Maintaining the e-flow represents a potential tool for restoring and managing river ecosystems, to preserve the autochthonous living communities, along with environmental services and cultural/societal values. In the last decade, methods for the determination of the e-flow in European rivers moved from a simply hydrological approach towards establishing a linkage between the hydrological regime and the good ecological status (GES) of the water bodies, as identified by the European Water Framework Directive (WFD; 2000/60/EC). Each Member State is required to implement and integrate into the River Basin Management Plans (RBMP) a methodology for the determination of the e-flow, ensuring that rivers can achieve and maintain the GES. The competent river basin authorities have thus to ascertain whether national methodologies to can be applied to different river typologies and basin environment characteristics. In this context, we narratively review the e-flow assessments in the heterogeneous Italian territory, in particular on a water scant region such as Sardinia, by analysing laws, guidelines and focusing on study cases conducted with micro and meso-scale hydraulic-habitat approaches. In the sight of a more ecological-based application of national e-flow policy, we suggest that meso-habitat methods provide a valuable tool to overcome several limitations of current e-flow implementation in the Italian territory. However, to face future challenges, such as climate change adaptation, we stress the need for further experimental studies to update water management plans with greater attention for nature conservation.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.8677
Cyanotoxins are a global concern in freshwaters and eutrophication and climate changes can have synergistic effects in exacerbating the problem. Deep Subalpine Lakes (DSL) are a group of lakes of huge economic and naturalistic importance in Italy. Together with eutrophication (occurred during 1960s and 1970s) and re-oligotrophication (from 1990 onward) these lake have been experiencing warming and increase of the water column stability. These changes have influenced the phytoplankton (comprised the cyanobacteria) community of the lakes. Four DSL lakes (Lakes Garda, Iseo, Como and Lugano) have been studied with the aim of comparing their toxic potential. For one of them (Lake Garda) an 8 years survey was conducted, allowing a long term trend analysis. Toxin analysis was conducted on a monthly basis by targeted LC-MS/MS. A screening for anatoxins, cylindrospermopsins, saxitoxins, microcystins (MCs) and nodularins was carried out. Among all the listed toxins, only one anatoxin and five MCs were detected in the lakes. In particular, the alkaloid Anatoxin-a (ATX) was found dominant Lakes Garda, Iseo and Como and absent in lake Lugano; the MC-[D-Asp3]RR was found as the most abundant MC in all four lakes. Four other minoritary MCs were also found. The two major toxins are produced by two different cyanobacteria (Tychonema bourrellyi and Planktothrix rubescens) which have however similar ecological traits. Peaks of these toxins occur in warmer months (typically between May and September) in the thermocline layer (around 20 m, in the considered lakes). In summer 2016, the highest concentrations of ATX and total microcystins (MCs) were registered in Lake Iseo (1100 and 430ngL-1, respectively), while in the other lakes values were approximately twice lower. In the lakes where it is present, ATX peak levels are much higher than MCs, thus highlighting the necessity of considering ATX in the procedures of risk assessment. The importance of ATX is expected to further grow in the future with respect to MCs, as demonstrated by the long term trend analysis carried out in Lake Garda that showed a clear decline for MCs from 2009 till 2016 and a relative constancy for ATX.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.8743
Due to specific environmental and ecological conditions, mangrove forests are known as marine transitional zones between sea and land, and, as such, they host organisms with high ecological plasticity. The mangrove forests of Qeshm Island (Iran) are relatively pristine habitats and represent an ideal target for investigating patterns of either aquatic or benthic biodiversity. To provide insights on microbial diversity in this area, nineteen halophilic and halotolerant bacteria were isolated from the sediments in 2017 during low tide. The extracted bacterial strains were studied morphologically by streaking, initial observation of colonies and bacterial staining, and characterized using a battery of biochemical tests including KOH, MR, VP, urease, TSI, S/I/M, Mac, LIA, ODC, ADH, oxidase, catalase, and tryptophan deaminase. The optimum growth of halophilic bacteria was observed in salt concentrations from 5 to 20% NaCl, whereas the extreme halophilic Gram-positive strain grew in salt concentration of up to 30% NaCl. Molecular analyses were also carried out on four halophilic strains and one extreme halophilic gram-positive bacteria. Phylogenetic taxonomy analysis, after 16S rDNA gene Sanger sequencing, revealed that the halophilic bacteria were closely related to the strain types of the genus Bacillus including Bacillus licheniformis, Bacillus velezensis, Bacillus Paralicheniformis and Bacillus sp. with 99% bootstrap value. The extreme halophilic strain was associated to strains of Planococcus plakortidis with 100% bootstrap value.
Advances in Oceanography and Limnology, Volume 11; https://doi.org/10.4081/aiol.2020.8961
Transitional waters are subject to a high degree of variability in space and time. In this study, protist plankton communities of the Lagoon of Venice were compared among four sites characterised by different environmental conditions with a metabarcoding approach. High throughput sequencing (HTS) of the V4-18S rDNA fragment in 32 samples collected on four dates, from April 2016 to February 2017, produced 1,137,113 reads, which were grouped into 4,058 OTUs at 97% similarity. Bacillariophyta and Ciliophora were the most abundant groups in the entire dataset in terms of read number (27.6% and 16.6%, respectively), followed by Dinophyta (10.9%), Cryptophyceae (9.7%), and Syndiniales (6.1%). The contribution of protist groups markedly varied across the seasons, but spatial differences were also recorded in the lagoon. In April, a higher contribution of Bacillariophyta characterized St1 and 5 (68.0% and 61.1%), whereas Sts2 and 3 showed a higher percentage of Ciliophora (18.6 and 23.4%, respectively) and dinoflagellates (10.3 and 7.7%). In July, diatom blooms occurred at Sts1, 2 and 3, with some differences in the dominant species. At St2 Dinophyta reached the highest contribution of the whole sampling period in the area (30.6%), while St5 was quite distinct, with a low contribution of diatoms and a dominance of Ciliophora (34.0%) and Trebouxiophyceae (36.4%). All the stations in November were characterized by relatively high abundance of Ciliophora (21.4-51.9%). In February, diatom contribution was relevant only at St5 (29.3%), Teleaulax acuta peaked at St3 (ca. 36%), Syndiniales at St2 (38.8%) and Dictyochophyceae at St1 (24.2%). The α-diversity indexes (observed OTUs, Shannon and Pielou evenness) showed a high variability over space and time. Overall, diversity and community composition were rather similar between the intermediate and deeper Sts2 and 3 on all sampling dates whereas they at time differed between the landward and shallow Sts1 and 5. While the most marked differences occurred over the temporal scale, the depth of the station and the relatedness with the external marine coastal environment appear to play a major role in the spatial distribution of protist communities within the lagoon.