Search results for "ocean"

Economic modelling as a tool to support macroalgal bloom management: a case study (Sacca di Goro, Po river delta)

2003

During the last 20, years, intensive mollusk farming has been developed in coastal waters, mostly in sheltered bays and lagoons. Often, mollusk stocks are threatened by frequent anoxic events from macroalgal blooms. Here, a decision support tool is described to select the optimal short-term strategy to control algal biomasses. Even though long-term and detailed studies of the lagoon systems are required to provide reliable, biologically based policies, we have here developed a simplified analysis that overlooks most of the ecological complexity, but explicitly includes environmental variability and uncertainty in parameter estimation in the economic assessment of the performances of differe…

The revolution of crossdating in marine palaeoecology and palaeoclimatology.

2019

Over the past century, the dendrochronology technique of crossdating has been widely used to generate a global network of tree-ring chronologies that serves as a leading indicator of environmental variability and change. Only recently, however, has this same approach been applied to growth increments in calcified structures of bivalves, fish and corals in the world's oceans. As in trees, these crossdated marine chronologies are well replicated, annually resolved and absolutely dated, providing uninterrupted multi-decadal to millennial histories of ocean palaeoclimatic and palaeoecological processes. Moreover, they span an extensive geographical range, multiple trophic levels, habitats and f…

Modelling circulation in an ice-covered lake

2010

In deep ice-covered lakes with temperatures below 4 °C the heat flux from the bottom sediment results in a horizontal density gradient and a consequent flow along the bottom slope. Measurements in Lake Paajarvi, Finland, show a stable temperature field where a heat gain through the bottom and a heat loss through the ice nearly balance each other. The circulation is thermal with low velocities (less than 1.5 cm s -1 ). We used the 3D hydrodynamic Princeton Ocean Model as a tool to simulate the water circulation and the temperature distribution under the ice. The model forcing was based on field temperature measurements. The model simulations suggest that in midwinter the velocity field of th…

The influence of lipid content and taxonomic affiliation on methane and carbon dioxide production from phytoplankton biomass in lake sediment

2021

Niche partitioning amongst northwestern Mediterranean cetaceans using stable isotopes

2021

Abstract Ten species of cetaceans coexist in the Mediterranean Sea, one of the richest seas in biodiversity and endemisms worldwide. The conservation status of Mediterranean cetaceans has been a concern for many years, particularly due to increasing anthropogenic threats such as global warming and overfishing. We established the stable isotopic niches of carbon, nitrogen, and sulphur for five species of cetaceans inhabiting the northwestern Mediterranean Sea to elucidate the mechanisms of coexistence. The fin whale exploited epipelagic habitats with a low trophic level; the bottlenose dolphin was mostly neritic and had a high trophic level; the Risso’s dolphin was oceanic and fed bathypelag…

The mapping of the Posidonia oceanica (L.) Delile barrier reef meadow in the southeastern Gulf of Tunis (Tunisia)

2016

Abstract Barrier reefs are among the most important ecomorphosis for Posidonia oceanica meadows and have long been subjected to anthropic pressures. The authors mapped the entire Sidi Rais (northeastern Tunisia) Posidonia oceanica barrier reef by means of remote sensing based on processing a satellite image acquired via Google Earth © software, coupled with field observations obtained by snorkeling. The map thus produced represents the P. oceanica barrier reef in its current state, covering a total area of 156.77 ha, the reef being divided into three distinct sections separated by reverse flows with each section subject to varied anthropic factors and disturbances.

Environmental sensitivity of Neogoniolithon Brassica-Florida associated with vermetid reefs in the Mediterranean Sea

2016

Vermetid reefs in the Mediterranean Sea are increasingly affected by both anthropogenic actions and global climate change, which are putting this coastal ecosystem at risk. The main species involved in building these reefs are two species of intertidal vermetid gastropods and the crustose calcareous alga, Neogoniolithon brassica-florida, which cements the gastropod shells and thus solidifying the reef edges. In the present study, we examined the pattern of distribution in the field and the environmental sensitivity (thermal tolerance, resilience to low pH, high light intensity and desiccation) of N. brassica-florida along the coasts of Sicily and Israel by means of chlorophyll fluorescence …

2021

Plankton assembly in an ultra-oligotrophic Antarctic lake over the summer transition from the ice-cover to ice-free period: A size spectra approach

2017

Abstract Lakes from the Antarctic maritime region experience climate change as a main stressor capable of modifying their plankton community structure and function, essentially because summer temperatures are commonly over the freezing point and the lake's ice cap thaws. This study was conducted in such seasonally ice-covered lake (Lake Limnopolar, Byers Peninsula, Livingston Is., Antarctica), which exhibits a microbial dominated pelagic food web. An important feature is also the occurrence of benthic mosses ( Drepanocladus longifolius ) covering the lake bottom. Plankton dynamics were investigated during the ice-thawing transition to the summer maximum. Both bacterioplankton and viral-like…

Decreasing in patch-size of Cystoseira forests reduces the diversity of their associated molluscan assemblage in Mediterranean rocky reefs

2021

Abstract Canopy-forming seaweeds of the genus Cystoseira (Fucales, Phaeophyceae) form diverse and productive habitats along temperate rocky coasts of the Mediterranean Sea. During the last decade, Cystoseira forests have retracted their range considerably due to many interacting environmental, biological and anthropogenic pressures. We investigated how reducing in patch-size of C. montagnei affects their associated molluscan communities at the shallow northwest rocky shores of Palermo (Sicily, Italy). Molluscs were sampled from the fronds of individual thalli, clumps of 3 and 5 thalli of C. montagnei over an annual vegetative cycle (May–September) in two sites within the Marine Protected Ar…