Mariachiara Chiantore

Forecasting the limits of resilience: integrating empirical research with theory

Despite the increasing evidence of drastic and profound changes in many ecosystems, often referred to as regime shifts, we have little ability to understand the processes that provide insurance against such change (resilience). Modelling studies have suggested that increased variance may foreshadow a regime shift, but this requires long-term data and knowledge of the functional links between key processes. Field-based research and ground-truthing is an essential part of the heuristic that marries theoretical and empirical research, but experimental studies of resilience are lagging behind theory, management and policy requirements. Empirically, ecological resilience must be understood in terms of community dynamics and the potential for small shifts in environmental forcing to break the feedbacks that support resilience. Here, we integrate recent theory and empirical data to identify ways we might define and understand potential thresholds in the resilience of nature, and thus the potential for regime shifts, by focusing on the roles of strong and weak interactions, linkages in meta-communities, and positive feedbacks between these and environmental drivers. The challenge to theoretical and field ecologists is to make the shift from hindsight to a more predictive science that is able to assist in the implementation of ecosystem-based management.

Trends in Ostreopsis proliferation along the Northern Mediterranean coasts

Harmful benthic microalgae blooms represent an emergent phenomenon in temperate zones, causing health, ecological and economic concern. The main goal of this work was to compile records of Ostreopsis at large temporal and spatial scales, in order to study the relationship between cell abundances, the periodicity and intensity of the blooms and the role of sea water temperature in 14 Spanish, French, Monegasque and Italian sites located along the northern limits of the Mediterranean Sea. General trends were observed in the two considered basins: the north-western Mediterranean Sea, in which higher cell abundances were mostly recorded in mid-summer (end of July), and the northern Adriatic Sea where they occur in early fall (end of September). The sea-water temperature does not seem to be a primary driver, and the maximal abundance periods were site and year specific. Such results represent an important step in the understanding of harmful benthic microalgae blooms in temperate areas, and provide a good base for policy makers and managers in the attempt to monitor and forecast benthic harmful microalgae blooms.

The toxic benthic dinoflagellate Ostreopsis ovata : Quantification of proliferation along the coastline of Genoa, Italy

Toxic harmful algal bloom (HAB) occurrence is becoming more frequent and problematic in highly urbanized coastal zones. In summer 2005 along the urbanized Genoa coastline (Ligurian Sea, North western Mediterranean Sea), local first aid stations treated about 200 people, who all showed similar symptoms following exposure to marine aerosols. The link with proliferation of Ostreopsis ovata was made, and it highlighted for the first time, the risks that benthic HABs may represent in highly urbanised temperate areas. Subsequently, a specific monitoring plan was designed and implemented in the same area in July 2006, before the first signs of Ostreopsis proliferation were detected. Here we report on this quantification of an Ostreopsis ovata bloom in the Ligurian Sea. Cells were quantified both in the water column and in the epiphytic community on macrophytes. Our results suggest a role of sea water temperature and weather conditions in favouring bloom development.

Toxic effects of harmful benthic dinoflagellate Ostreopsis ovata on invertebrate and vertebrate marine organisms

Harmful benthic microalgae blooms are an emerging phenomenon causing health and economic concern, especially in tourist areas. This is the case of the Mediterranean Sea, where Ostreopsis ovata blooms occur in summer, with increasing regularity. Ostreopsis species produce palytoxin (PTX) and analogues, and a number of deaths directly associated with the ingestion of PTX contaminated seafood have been reported. PTX is considered one of the most toxic molecules occurring in nature and can provoke severe and sometimes lethal intoxications in humans. So far in temperate areas, O. ovata blooms were reported to cause intoxications of humans by inhalation and irritations by contact. In addition, invertebrate mass mortalities have been reported, possibly linked to O. ovata blooms, although other causes cannot be ruled out, such as oxygen depletion or high seawater temperature. In order to improve our knowledge about the direct toxicity of this species on invertebrate and vertebrate marine organisms, we performed an ecotoxicological screening to investigate the toxic effects of different concentrations of O. ovata (cultured in the laboratory and sampled in the field during blooms) on crustaceans and fish as model organisms. Artemia salina, Tigriopus fulvus, and Amphibalanus amphitrite larvae and juveniles of the sea bass Dicentrarchus labrax were used as model species. Toxic effects associated with cultured O. ovata cells were investigated using a crossed design: testing two different temperatures (20 and 25 °C), four different cell concentrations, and four treatments (untreated O. ovata culture, filtered and resuspended algal cells, growth medium devoid of algal cells, and sonicated algal cells). The results indicate that the toxicity of cultured O. ovata is related to the presence of living O. ovata cells, and that this effect is amplified by temperature. Furthermore, both tests with laboratory cultured algae and field sampled cells pointed out that A. salina is the most sensitive species even at concentrations below the Environmental Alarm Threshold set by the Italian Ministry of Health. Some possible explanations of such sensitivity are discussed, taking into account evidence of O. ovata cells ingestion and the activity of its toxins on the Na⁺/K⁺-ATPase.

BACI design reveals the decline of the seagrass Posidonia oceanica induced by anchoring.

The key species Posidonia oceanica is the dominant endemic seagrass in the Mediterranean Sea and its meadows are considered as one of the most important and productive ecosystems in coastal waters. Covering the seabed from the surface down to about 40 m, meadows of P. oceanica are often affected by mechanical direct damages caused by boat anchoring and mooring activities. Negative effects of these activities have been shown to be recorded by P. oceanica at two different levels: the individual level (phenology of the plant) and the population level (structure of the meadow). We investigated the effect of an anchoring chain system on the P. oceanica meadow of Prelo cove (NW Mediterranean Sea) at two different depths (shallow, deep) and at three different situations of P. oceanica bottom cover (high, medium, low). Several standardized descriptors of the meadow health, working either at the individual or at the population level, were analysed in order to quantify the impact of the deployment of the chain system. A symmetrical BACI design was adopted to detect the impact, where multiple disturbed sites were contrasted with multiple controls in two distinct times, i.e. right few days after the chain settling (early) and 4 months later the disturbance (late). The anchoring chain system has been shown to strongly affect the meadow in terms of shoot density decline and rhizome baring, especially in the deep portions and where the cover of the meadow was low. All descriptors working at the population level proved effective in detecting the impact of the anchoring system. In contrast, descriptors working at the individual level did not show a consistent response to the impact. Our results pointed out the imperative necessity to proper regulate the boat anchoring and mooring activities on the P. oceanica meadows and the adoption of seagrass friendly mooring technology is thus recommended.

The Ligurian Sea: present status, problems and perspectives

The Ligurian Sea is a deep basin in the northernmost sector of the western Mediterranean which shows peculiar hydrodynamic and meteo-oceanographic features. The coasts of the Ligurian Sea are among the most urbanised and industrialised along the Italian coastline: the main causes of disturbance being littoral urban development and harbour activities, the building of littoral rail- and highways, and the presence of several polluted discharges. This review, by evaluating the huge scientific output published in the last three decades, describes and discusses the most important geological, hydrological and biological characteristics of the Ligurian Sea. We show that this regional sea has largely been investigated in terms of its geological and structural evolution, as well as in terms of the sedimentation dynamics of the littoral and deep bottoms, with particular attention to the sedimentation balance of the beaches and their erosive processes. We report that the prevalent hydrodynamic and meteo-oceanographic conditions favour a continuous exchange of coastal water masses, and that the seasonal and interannual dynamics of water masses can effects the local climate, with direct and indirect consequences on fish and benthic communities documented in the last decade. We stress that although recent studies offer good knowledge of the distribution of coastal benthic communities, only scant information is available for the whole continental shelf, the submarine canyons and the rocky bathyal bottoms. Our meta-analysis reveals that significant fishing activities are monitored, but also that certain sectors of the biological resource are suffering, and suggests the set up of appropriate management measures. The Ligurian Sea hosts a number of Marine Protected Areas (MPAs) of high relevance, while the institution of the Whale Sanctuary completes the protection policy of the Regione Liguria. Our meta-analysis points out the need for long-term studies, based primarily on the analysis of those areas of the Ligurian Sea that have been little investigated to date. Finally, only properly addressed studies, using experimental approaches and along appropriate spatial and temporal scales, might allow us to understand the functioning of the Ligurian marine ecosystems, evaluate their health conditions and the dynamics of the main variables that affect the distribution of the single species (including species of high economic value) and benthic communities.

Age and productivity of the Antarctic scallop, Adamussium colbecki, in Terra Nova Bay (Ross Sea, Antarctica)

Body size, geographical distribution and biomass make Adamussium colbecki (Smith 1902) one of the most important bivalve species in the Antarctic. Based on samples collected in austral summer 1999/2000 in Terra Nova Bay, the annual formation of shell growth bands visible on x-ray photographs was verified by stable isotope analyzis. A general von Bertalanffy growth function was fitted to size-at-age data of 25 individuals (H*= 108.86 mm, K= 0.114 y-1, t0= -0.367, D= 1.284). Maximum age of A. colbecki is likely to be more than 18 years. Somatic production calculated from mass-specific growth rates was 235 kJ m-2 y-1. Gonadal productivity estimated by an average value for reproductive output of pectinids amounted to 59 kJ m-2 y-1. Annual somatic and gonad production-to-biomass ratios (P/B) were 0.199 and 0.043, respectively. According to its consumption and production A. colbecki is likely to play a significant role in the trophic web of Terra Nova Bay.

Shallow- and deep-water mollusc distribution at Terra Nova Bay (Ross Sea, Antarctica)

Abstract The aim of this work is to improve the knowledge of the mollusc fauna of Terra Nova Bay (Ross Sea), on the basis of more than 100 stations sampled from 25 to 1100 m depth, during Italian Antarctic Expeditions (austral summers 1987/1988, 1989/1990, 1993/1994, 1994/1995, 1995/1996 and 1997/1998). In shallow waters, gastropod fauna is represented by 31 species, among which Neobuccinum eatoni, Onoba gelida, Powellisetia deserta, Philine cf. apertissima and Austrodoris kerguelenensis are the most abundant, while among bivalves (25 species) the commonest species are Adamussium colbecki, Yoldia eightsi, Laternula elliptica and “Montacuta”nimrodiana. At present, most of the Antarctic mollusc species are known as having circumantarctic distribution and are considered eurybathic. Moreover, in general, only scarce data are available on their substrate preferences, because of their occurrence in scattered sampling stations with different sediment features. In the present study carried out at Terra Nova Bay, based on a relatively high number of stations, a clear zonation of mollusc assemblages is shown, according to depth and sediment features. While gastropods characterise the superficial algal belts dominated by the red algae Iridaea cordata and Phyllophora antarctica, bivalve distribution is wider. Adamussium colbecki is the dominant species in the upper 100 m, both on soft and hard bottoms, if the slope is suitable (density up to 40–60 ind./m2). On coarse sands, this species is frequently accompanied by L. elliptica (density <20 ind./m2), while Y. eightsi characterises organic- enriched bottoms (density 70–80 ind./m2). Below 200 m depth Adacnarca nitens, Limatula hodgsoni, “Montacuta”nimrodiana and Mysella gibbosa are commonly found on relatively coarse sediments, while Thyasira dearborni and Yoldiella ecaudata prefer muddy bottoms. In order to identify bivalve assemblages, multivariate analyses were applied to stations grouped into depth ranges, sediment features and location. While shallow bathymetric ranges (25–200 m) are clearly defined, deeper clusters of stations are more influenced by the high degree of eurybathy of most of the species and by the scattered distribution of the sediment particle sizes.

Short-term variations in particulate matter flux in Terra Nova Bay, Ross Sea

As part of the Ross Sea Marginal Ice Zone Ecology Project (ROSSMIZE) the summer organic matter flux through the water column was measured at 40 m depth in Terra Nova Bay. Water samples and material from a sediment trap on the sea-bottom were analysed for their biochemical composition. A close coupling between biochemical composition of the organic matter in the water column and the material collected in the sediment trap was found, resulting from complex interactions between physical and biological processes. The physical processes are related to break-up and melting of the ice cover and occur mainly in the early summer season, whilst biological processes play a key role in mid summer and, from the evidence from faecal pellets, are related to the primary production and consumption processes.

Temperature effects on summer growth rates in the Antarctic scallop, Adamussium colbecki

Annual growth rates of Antarctic marine organisms are low compared to their relatives from warmer waters. Previous studies hypothesise that high food availability during austral spring–summer may enable Antarctic invertebrates to attain comparatively high short-term growth rates despite the low temperature. Neither a temperature-growth experiment with juvenile Adamussium colbecki (Smith 1902) nor the comparison of A. colbecki summer growth rates with an empirical scallop specific growth-to-temperature relationship could confirm this hypothesis. Hence, summer growth rates of young, immature A. colbecki are strongly affected by temperature, i.e. no “uncoupling” from temperature.