Evaluating the role of seagrass in Cenozoic CO2 variations

Marine seagrass angiosperms play an important role in carbon sequestration, removing carbon dioxide from the atmosphere and binding it as organic matter. Carbon is stored in the plants themselves, but also in the sediments both in inorganic and organic forms. The inorganic component is represented by carbonates produced by calcareous organisms living as epiphytes on seagrass leaves and rhizomes. In this paper, we find that the rate of seagrass epiphyte production (leaves and rhizomes) averages 400 g m−2 yr−1 , as result of seagrass sampling at seven localities along the Mediterranean coasts, and related laboratory analysis. Seagrasses have appeared in the Late Cretaceous becoming a place of remarkable carbonate production and C sequestration during the whole Cenozoic era. Here, we explore the potential contribution of seagrass as C sink on the atmospheric CO2 decrease by measuring changes in seagrass extent, which is directly associated with variations in the global coastal length associated with plate tectonics. We claim that global seagrass distribution significantly affected the atmospheric composition, particularly at the Eocene-Oligocene boundary, when the CO2 concentration fell to 400 ppm, i.e., the approximate value of current atmospheric CO2

Nitrogen uptake and internal recycling in Zostera marina exposed to oyster farming: eelgrass potential as a natural biofilter

Oyster farming in estuaries and coastal lagoons frequently overlaps with the distribution of seagrass meadows, yet there are few studies on how this aquaculture practice affects seagrass physiology. We compared in situ nitrogen uptake and the productivity of Zostera marina shoots growing near off-bottom longlines and at a site not affected by oyster farming in San Quintin Bay, a coastal lagoon in Baja California, Mexico. We used benthic chambers to measure leaf NH4 (+) uptake capacities by pulse labeling with (NH4)-N-15 (+) and plant photosynthesis and respiration. The internal N-15 resorption/recycling was measured in shoots 2 weeks after incubations. The natural isotopic composition of eelgrass tissues and vegetative descriptors were also examined. Plants growing at the oyster farming site showed a higher leaf NH4 (+) uptake rate (33.1 mmol NH4 (+) m(-2) day(-1)) relative to those not exposed to oyster cultures (25.6 mmol NH4 (+) m(-2) day(-1)). We calculated that an eelgrass meadow of 15-16 ha (which represents only about 3-4 % of the subtidal eelgrass meadow cover in the western arm of the lagoon) can potentially incorporate the total amount of NH4 (+) excreted by oysters (similar to 5.2 x 10(6) mmol NH4 (+) day(-1)). This highlights the potential of eelgrass to act as a natural biofilter for the NH4 (+) produced by oyster farming. Shoots exposed to oysters were more efficient in re-utilizing the internal N-15 into the growth of new leaf tissues or to translocate it to belowground tissues. Photosynthetic rates were greater in shoots exposed to oysters, which is consistent with higher NH4 (+) uptake and less negative delta C-13 values. Vegetative production (shoot size, leaf growth) was also higher in these shoots. Aboveground/belowground biomass ratio was lower in eelgrass beds not directly influenced by oyster farms, likely related to the higher investment in belowground biomass to incorporate sedimentary nutrients

Proceedings of the Mediterranean Seagrass Workshop 2006

The Mediterranean Seagrass Workshop 2006 was convened in response to the need to promote a periodic event that would host scientists interested in Mediter- ranean seagrasses, and international scientists who are involved in projects that are focused on the Mediterranean marine environment, to discuss current knowl- edge and present the findings of their latest research. The concept of holding an international meeting originated during the Inter- national Seagrass Biology Workshop (ISBW6) held in 2004 in Queensland, Aus- tralia. In particular, one of the goals of ISBW6 was to identify key ecological issues and environmental trends within a number of geographical regions. This stimulated the idea of taking such topic to a higher level; the Mediterranean scale. The Mediterranean Sea is a rare and vulnerable ecoregion, one of the planet’s biodiversity hot spots, where many of the species present are endemic (around 20%). The Mediterranean Sea also has a millenarian history of human use of its coasts. However, the current exponential increase of human pressure on the coastal zone for living space, transportation, recreation and food production is expected to have dramatic long-term impacts on the Mediterranean marine envi- ronment. Being located in shallow coastal areas close to human settlement, sea- grasses are bearing the brunt of disturbance from such anthropogenic activities, with the result that degradation and loss of seagrass habitats is widespread in the whole Mediterranean Sea. Thus, there is great concern that the functions which seagrasses have performed in the Mediterranean marine ecosystem will be weak- ened or, in some places, lost altogether.peer-reviewe

Recognition and assessment of seafloor vegetation using a single beam echosounder

This study focuses on the potential of using a single beam echosounder as a tool for recognition and assessment of seafloor vegetation. Seafloor vegetation is plant benthos and occupies a large portion of the shallow coastal bottoms. It plays a key role in maintaining the ecological balance by influencing the marine and terrestrial worlds through interactions with its surrounding environment. Understanding of its existence on the seafloor is essential for environmental managers.Due to the important role of seafloor vegetation to the environment, a detailed investigation of acoustic methods that can provide effective recognition and assessment of the seafloor vegetation by using available sonar systems is necessary. One of the frequently adopted approaches to the understanding of ocean environment is through the mapping of the seafloor. Available acoustic techniques vary in kinds and are used for different purposes. Because of the wide scope of available techniques and methods which can be employed in the field, this study has limited itself to sonar techniques of normal incidence configuration relative to seafloors in selected regions and for particular marine habitats. For this study, a single beam echosounder operating at two frequencies was employed. Integrated with the echosounder was a synchronized optical system. The synchronization mechanism between the acoustic and optical systems provided capabilities to have very accurate groundtruth recordings for the acoustic data, which were then utilized as a supervised training data set for the recognition of seafloor vegetation.In this study, results acquired and conclusions made were all based on the comparison against the photographic recordings. The conclusion drawn from this investigation is only as accurate as within the selected habitat types and within very shallow water regions.In order to complete this study, detailed studies of literature and deliberately designed field experiments were carried out. Acoustic data classified with the help of the synchronized optical system were investigated by several methods. Conventional methods such as statistics and multivariate analyses were examined. Conventional methods for the recognition of the collected data gave some useful results but were found to have limited capabilities. When seeking for more robust methods, an alternative approach, Genetic Programming (GP), was tested on the same data set for comparison. Ultimately, the investigation aims to understand potential methods which can be effective in differentiating the acoustic backscatter signals of the habitats observed and subsequently distinguishing between the habitats involved in this study

The effect of leaf movement on algal epiphytes in seagrass meadows

Artificial seagrass units were used to determine whether seagrass leaf movement influences the biomass, species richness and composition of epiphytic macroalgae on the leaves of seagrasses, and whether the influence of leaf movement is altered by the degree of exposure to water movement and to depth. The influence of leaf movement on epiphytic biomass is important from an environmental management perspective, as there is the potential for epiphytic productivity to be underestimated if leaf movement is reducing the standing crop of epiphytes on seagrass leaves. Two forms of artificial seagrass units were used in three experiments to achieve these objectives; untethered units mimicked natural seagrass leaves, that were free to move in response to water movement, and tethered units mimicked seagrass leaves that were unable to move. The first experiment examined the effect of seagrass movement on the biomass, species richness and species composition over time. The second and third experiments examined the influence of exposure and depth on the effect of seagrass leaf movement on epiphytic biomass. In all three experiments the epiphytic biomass, measured in terms of dry weight (DW) and ash free dry weight (AFDW), was far greater in tethered than untethered units, where the epiphytic biomass was on average eight times higher on tethered leaves. Similarly species richness was shown to be greater in tethered vs untethered units. These results provide clear evidence that the movement of seagrass leaves has a profound effect on the accumulation of epiphytic algae. In addition, ordination revealed clear differences in epiphytic species composition and species richness between the tethered and untethered units, and over time. Algae of the genus Hypnea were characteristic of tethered leaves, while Griffithsia australe and Antithamnion spp. were characteristic of untethered units. Untethered leaves at sheltered and exposed sites showed no difference in epiphytic biomass. The results also showed that there was no difference in epiphytic biomass on the untethered leaves between deep and shallow sites but that tethered leaves had a significant higher biomass at shallow depths. The results of this study provide strong evidence that the movement of seagrass leaves strongly influences the biomass, species richness and species composition of epiphytic algae. However, it is not as clear whether the process of leaf movement is reducing the standing crop of epiphytes through abrasion, or if leaf movement is in fact inhibiting the settlement of propagules onto the seagrass leaves. If leaf movement results in an abrasional loss of epiphytic algae, previous studies may have underestimated epiphytic production in our seagrass meadows, thus the production of seagrass ecosystems and their inherent value. However, if leaf movement is instead limiting the settlement of propagules then the underestimation of epiphytic productivity is not as likely

A first survey on the status of the Posidonia oceanica meadow in Calpe Bay (Alicante, Spain).

Posidonia oceanica, endemic seagrass of the Mediterranean Sea, forms extensive meadows. It is included among the Mediterranean protected habitats by the Habitat Directive (92/43/EEC). P. oceanica meadows are exposed to anthropogenic impacts that are more evident in areas close to cities, ports or areas with a large coastal tourism development. Mean exponential decline rate of 5 % yr-1 is estimated for the Spanish meadows. If this trend is maintained, most of the meadows are predicted to halve in shoot density over the next 20 years. The meadows regression can give way to a new regime, which supposes the loss of the multiple services that the meadows provided. It is necessary to recognize situations of stress in time, before irreversible damages and changes towards alternative regimes are evident. This study has been carried out in Calpe Bay, Alicante (Spain), during May and June 2017, with the aim of assessing, for the first time, the status of the P. oceanica meadows providing a baseline data for the future monitoring scheme. The features and status of the seagrass beds have been assessed by physical, physiographical, structural and functional descriptors. The results showed that the health status classification of P. oceanica meadows in Calpe Bay vary between “equilibrium” and “disturbed”. The “disturbed” conditions were observed in a shaded area where it is probably due to the low solar radiance. In a lower limit in a shallow meadow, where it could be due to the combined effect of substrate structure and hydrodynamic regime. Finally in a touristic area where patchy impacts could be attributed to direct human disturbance (e.g. anchoring). Overall the status of P. oceanica meadows in Calpe bay is not worrying. However, it is important to develop monitoring plans to assess the dynamics of the seagrass detecting any early decline symptom in order to act, as soon as possible because, when a regression of a meadow is produced, it could not be recovered at human scales

Compilation of an interpretation manual for marine habitats within the 25 NM Fisheries Management Zone around the Republic of Malta

Several EU Directives and regional conventions are concerned with the protection and conservation of marine habitats of special importance; a necessary prerequisite to implement such legislation are marine habitat classification systems and information on the distribution of marine habitat types. There are several habitat classification schemes in use for the description, designation and monitoring of habitats. The ‘Interpretation Manual for Marine Habitats within the 25 NM Fisheries Management Zone around the Republic of Malta’ provides an updated description of marine habitats found around the Maltese Islands, as well as a cross-referencing scheme for the different habitat classification systems. Marine habitats are listed according to bathymetric zone, going from shallow to deep water. The bathymetric zones included in the interpretation manual are: (1) mediolittoral, (2) infralittoral, (3) circalittoral, and (4) bathyal. Habitats listed in the European Nature Information System (EUNIS) database were reviewed, habitats which are present in the Maltese Islands were identified, and ‘new’ habitat categories have been included in the manual where there was no equivalent EUNIS habitat. For each habitat category presented, cross- references to the system used in connection with the Protocol for Specially Protected Areas and Biodiversity in the Mediterranean (SPABM) of the Barcelona Convention, to the Marine Strategy Framework Directive (MSFD) classification system of predominant habitat types, as well as to the marine habitats listed in Annex I of the ‘Habitats Directive’, were established. In addition a scheme to enable the assessment of the conservation status of marine habitats as required under the ‘Habitats Directive’ was drawn up by considering the habitat range, the area occupied by a habitat, habitat structure and function, and the habitat’s future prospects. Suitable indicators to assess favourable conservation status are presented for (i) sandbanks, (ii) Posidonia beds, (iii) reefs and (iv) sea caves. In addition, indicators to assess the conservation status of maerl beds are presented due to the local significance and the sensitivity of this habitat. The manual thus intends to aid in the implementation of measures for the protection of marine habitats and hence, ultimately, to ensure effective and efficient management of the marine environment under the jurisdiction of Malta up to the 25 NM boundary, in line with the relevant legislation.peer-reviewe

Seagrass macrophytodetritus : a copepod hub: species diversity, dynamics and trophic ecology of the meiofauna community in Posidonia oceanica leaf litter accumulations

Macrophytodetritus is a heterogeneous mixture of detrital material that accumulates on submerged unvegetated sand patches amid vast Mediterranean Posidonia oceanica seagrass meadows. Several vagile invertebrates are present in substantial biomass and biodiversity. Among these invertebrates, meiofauna (fauna between 38µm and 1mm) is ubiquitous and seems to play a key-feature in this dynamic and patchy system. Coastal ecosystems are under the direct effect of anthropogenic disturbance and degradation. Extra research is crucially needed to understand better the dynamics of coastal vegetation, in order to have a more successful restauration of these regressing ecosystems. In this context, the main goal of this PhD research was triple: (1) characterising in situ the physico-chemistry and the composition of the macrophytodetritus accumulations in the Calvi Bay, Corsica, (2) identifying the diversity of the associated meiofauna communities, especially harpacticoid copepods together with unravelling the origin of the present copepods and (3) characterizing the trophic ecology of the copepod communities in the macrophytodetritus at the specific and eco-morphological level. This research showed that macrophytodetritus biomass is composed on average for 75% of dead P. oceanica seagrass leaves shed after senescence. Attached to the surface of the seagrass leaves numerous micro- and macroepiphytes are present, representing on average 10% of the total biomass. The remaining part is mainly constituted of drift material, like detached P. oceanica shoots and epilithic macroalgae. A seasonal pattern is observed regarding the amount of accumulated material and the physico-chemical composition inside the accumulation. Wind-induced hydrodynamics is the responsible driver behind the variability of the macrophytodetritus and consequently it has a major impact on the faunal communities already present in a macrophytodetritus accumulation. Previous studies showed that the presence of macrofaunal invertebrates (> 1 mm) in high amounts contributes to the degradation of the detritus. Similarly, this study proves the ubiquitous presence of meiofauna in macrophytodetritus. Depending on the season, densities from 20.10³ to 160.10³ meiofaunal organisms per square metre of accumulation were recorded. Copepods were the most abundant taxon (> 50%) of which 87% belonged to the order Harpacticoida. Nematodes were the second most abundant taxon, representing on average 18% of the total meiofauna densities. A total of 61 copepod species were found in Calvi Bay macrophytodetritus accumulations and adjacent habitats (bare sand, seagrass and water column), wherefrom 85% were shared amongst these habitats, underlining the high colonization capabilities of copepods. Active colonization occurred within 24h through species-specific dispersal pathways. Certain species were more avid to colonize, resulting in a colonizer-competitor trade-off among the copepod community. Eco-morphological characteristics seemed to be responsible for the dispersal potential. However, the variety of the composition of the copepod community suggested that other factors also contributed to the attractiveness of the structurally complex macrophytodetritus habitat. The isotopic niches of four abundant copepod species, representing four different eco-morphological groups were identified: Ectinosoma dentatum (mesopsammic-type), Diosaccus tenuiremis (phytal-type), Tisbe furcata (epibenthic-type) and Clausocalanus arcuicornis (water-column-type). Based on stable isotope analysis, fatty acid profiling and Bayesian mixing model, results suggested an interspecific diversity which would indicate a species-specific resource partitioning. C. arcuicornis mainly fed on suspended organic matter, while D. tenuiremis thrived mainly on epiphytes (mostly diatoms). E. dentatum was dependent on the seasonal availability of food sources, while T. furcata fed on a heterogeneous mixture of sources. Presumably none of the species directly assimilated dead seagrass leaf litter. Overall, by combining in situ sampling, novel mesocosm experiment, biomarkers and mixing models, this study displayed the carrying capacity of macrophytodetritus to support a large amount of meiofauna and a wide diversity of copepod species. The morphological differences among copepod species seem to allow specialization towards habitat preferences, (physical habitat preferences and colonization potential) and towards resource preferences (food partitioning). Macrophytodetritus seems thus to be a suitable home, or a temporary hub for a diverse copepod community. Finally, this dynamic and patchy habitat, prone to swift changes and situated at the crossing of different ecosystems, plays a major role in coastal ecology

PALAEONTOLOGY OF THE UPPER PLIOCENE MARINE DEPOSITS OF RIO VACCARUZZA, VILLALVERNIA (PIEDMONT, NW ITALY)

Abstract. The topmost Argille Azzurre (beds 1-2) and the basal Sabbie di Asti (beds 3-9) formations in the Villalvernia area are analysed in terms of palaeoecological and taxonomic features; the succession is 6 m thick and dates back to the middle Piacenzian within the Globorotalia bononiensis acme. The upper boundary of the clayey Bed 2 corresponds to an unconformity reflecting Pliocene tectonic activity. The study is focused on the fossil assemblages of beds 3, 4 and 9. The sandy Bed 3 yields 362 mollusc taxa; their assemblage is allochthonous and mixes infra- to circalittoral species accumulated by hyperpycnal mass-transport. The same mechanism is responsible for the origin of the overlying fossil unit (Bed 4) with numerous specimens of the Entobia-Gastrochaenolites ichnofacies. The autochthonous fossil assemblage of Bed 9 yields 308 molluscs, plus three brachiopods and ten fish taxa; most of them refer to the Posidonia meadow (HP), and their autochthony is shown by taphonomic features as skeletal integrity, mixing of successive generations or the limitation to juvenile ontogenetic stages of vagile and temporarily byssate species for which the HP performs a nursery function. Three brachiopods and 52 molluscs are here reported for the first time from the Pliocene of Piedmont. In the final chapter “Systematic Palaeontology” four brachiopods and 29 molluscs are described, among which there are eight new gastropod species: Crepidula bellardii n. sp., Conus dellabellai n. sp., Conus villalvernensis n. sp., Odetta chirlii n. sp., Ondina curta n. sp., Ondina elongata n. sp., Ondina pseudovitrea n. sp., Anisocycla subcylindrica n. sp

Seagrasses benefit from mild anthropogenic nutrient additions

Seagrasses are declining globally, in large part due to increased anthropogenic coastal nutrient loads that enhance smothering by macroalgae, attenuate light, and are toxic when in excessive concentrations of inorganic nitrogen and phosphorus. However, as sanitation is improved many seagrass meadows have been observed to recover, with a few studies suggesting that they may even benefit from mild anthropogenic nutrient additions. Monitoring seagrass demography and health has faced difficulties in establishing the adequate variables and metrics. Such uncertainty in the methods has caused uncertainty of the significance of results presented and compromised extrapolations to other seasons, areas, or species. One solution has come from within the plant self-thinning theories. During the 1980s, an interspecific boundary line (IBL) was determined as the upper limit of the combination of plant density and above-ground biomass for any stand on Earth, setting their maximum possible efficiency in space occupation. Recently, two meta-analyses to determine specific IBLs for algae and for seagrasses have been performed. The recently updated seagrass dataset comprises 5,052 observations from 78 studies on 18 species. These IBLs opened new perspectives for monitoring: the observed distance of a stand to the respective IBL (i.e., each stand's relative efficiency of space occupation) was demonstrated to be a valuable indicator of a population's health. Thus, this metric can be used to determine the impact of nutrients and pollutants on algae and seagrass populations. Furthermore, because the IBLs are common to all species, they may be used to compare all species from any location worldwide. This novel approach showed that Halodule wrightii, Halodule beaudettei, Halophila baillonii, Zostera marina, and Zostera noltei meadows benefit from anthropogenic additions of nitrogen and phosphorus, as long as these additions are moderate. In fact, the healthier Z. noltei meadows in Portugal (and among the healthiest meadows worldwide) were the ones exposed to effluents from wastewater treatment plants (WWTP) and a food factory. We conclude that those effluents are providing water with enough quality and that their optimal management should coordinate the technological solutions of the WWTP with the natural potential of seagrass meadows as water purifiers and biomass producers.info:eu-repo/semantics/publishedVersio