1,738 publications from this institution
– is immense, and they are also the primevalscenario for the diversification of life. Thus the oldest known fossils aremarine stromatolites, laminar structures produced by the activity ofcyanobacteria, preserved in Australia and dating back 3,500 million years.Seemingly, the first animals also appeared in the sea. We know of trace fossils800 million year old, but the first fossils of “real” animals are dated later; about640 million years ago at the end of the Proterozoic period. These animalsbelong to the so-called “Ediacara” fauna of the Vendian system, a name whichrecalls the Australian locality where they were discovered, although they arealso present in other parts of the globe. They were soft-bodied organisms thatare hard to attribute to any of our modern types.In comparison, the earliest ter restrial fossil record corresponds to spores, pos-sibly of bryophytes (mosses, liverworts, etc.) and is datable to the MiddleOrdovician (about 450 million years ago). For animals, the first continentalsettlement appears to go back to the Silurian period (a bit over 400 millionyears ago), from which we have recovered remains of myriapods (centipedesand millipedes) and arachnids, although certain trace fossils, probably pro-duced by terrestrial arthropods, also date to the Ordovician period.Marine organisms have thus had more time to diversify than their terrestrialcounterparts (about double in the case of animals). And yet the oceans appar-ently harbour only 2% of the total number of known animal species. Scien-tists have resorted to different
Giant clams (Subfamily Tridacninae), are important members of Indo-Pacific coral reefs, playing multiple roles in the framework of these communities. Although they are prominent species in Red Sea reefs, data on their distribution and densities in the region are scarce. The present study provides the first large-scale survey of Red Sea Tridacna spp. densities, where we examined a large proportion of the Saudi Arabian Red Sea coast (1,300 km; from 18° to 29°N). Overall, Tridacninae were found at densities of 0.19 ± 0.43 individuals m –2 (±SD). Out of the total 4,002 observed clams, the majority (89%) were Tridacna maxima , with 0.17 ± 0.37 individuals m –2 , while only 11% were Tridacna squamosa clams with 0.02 ± 0.07 individuals m –2 . We also report on a few (total 6) Tridacna squamosina specimens, found at a single reef. We identified different geographical parameters (i.e., latitude and distance to shore) and local environmental factors (i.e., depth and reef zone) as the main drivers for local Tridacna spp. densities. Our results show that the drivers influencing the densities of Red Sea giant clams are complex due to their co-occurrence and that this complexity might explain the high variation in Tridacninae abundances across the Indo-Pacific, but also within a given reef. We also estimate that giant clam calcification likely contributes to an average of 0.7%, but potentially up to 9%, of the overall mean calcium carbonate budget of Red Sea coral reef communities.
Abstract The hypothesis that seaweed farming contributes to carbon burial below the farms was tested by quantifying burial rates in 20 seaweed farms distributed globally, ranging from 2 to 300 years in operation and from 1 ha to 15,000 ha in size. This involved combining analyses of organic carbon density with sediment accumulation rate in sediments below seaweed farms relative to reference sediments beyond the farm and/or prior to the farm operation. One in every four farms sampled was set over environments that export, rather than retain materials. For the farms that were placed over depositional environments, where sediment accumulation could be quantified, the thickness of sediment layers and stocks of carbon accumulated below the farms increased with farm age, reaching 140 ton C ha -1 for the oldest farm, and tended to exceed those in reference sediments beyond the farm and/or prior to the operation of the farms. Organic carbon burial rates in the farm sediments averaged (± SE) 1.87 ± 0.73 ton CO 2 equivalent (CO 2-eq ) ha -1 year -1 (median 0.83, range 0.10 – 8.99 ton CO 2-eq ha -1 year -1 ), twice the average (± SE) burial rate in reference sediments (0.90 ± 0.27, median 0.64, range 0.10-3.00 ton CO 2-eq ha -1 year -1 ), so that the excess organic carbon burial attributable to the seaweed farms averaged 1.06 ± 0.74 ton CO 2-eq ha -1 year -1 (median 0.09, range −0.13-8.10 ton CO 2-eq ha -1 year -1 ). This first direct quantification of carbon burial in sediments below seaweed farms confirms that, when placed over depositional environments, seaweed farming tend to sequester carbon in the underlying sediments, but do so at widely variable rates, increasing with farm yield.
Abstract Deoxygenation in coastal and open‐ocean ecosystems rarely exists in isolation but occurs concomitantly with acidification. Here, we first combine meta‐data of experimental assessments from across the globe to investigate the potential interactive impacts of deoxygenation and acidification on a broad range of marine taxa. We then characterize the differing degrees of deoxygenation and acidification tested in our dataset using a ratio between the partial pressure of oxygen and carbon dioxide ( p O 2 / p CO 2 ) to assess how biological processes change under an extensive, yet diverse range of p O 2 and p CO 2 conditions. The dataset comprised 375 experimental comparisons and revealed predominantly additive but variable effects (91.7%, additive; 6.0%, synergistic; and 2.3%, antagonistic) of the dual stressors, yielding negative impacts across almost all responses examined. Our data indicate that the p O 2 / p CO 2 ‐ratio offers a simplified metric to characterize the extremity of the concurrent stressors and shows that more severe impacts occurred when ratios represented more extreme deoxygenation and acidification conditions. Importantly, our analysis highlights the need to assess the concurrent impacts of deoxygenation and acidification on marine taxa and that assessments considering the impact of O 2 depletion alone will likely underestimate the impacts of deoxygenation events and their ecosystem‐wide consequences.
This study quantified climate-driven changes and spatial variability in key environmental drivers over four decades along Greenland's coastal and shelf marine ecosystems and evaluated their impacts on marine biota divided into six regions. We analyzed trends in sea ice concentration and seasonality, sea surface temperatures, salinity, and freshwater inputs from ice discharge and freshwater runoff. West, East, and Southeast Greenland were most impacted by climate change, driven by increasing sea surface temperatures (0.22-0.5 °C decade-1), freshwater inputs (10.14-24.93 Gt yr-1 decade-1), declining sea ice concentrations (3-5.3 % decade-1), and more open water days (10.92-23.9 days decade-1). The Northwest and Northeast regions appeared more resilient due to lower sea surface temperature increases (0.01-0.03 °C decade-1) and sea ice declines (0.5-2.1 % decade-1). Changes in Southwest Greenland were limited to sea surface temperature (0.27 °C decade-1) and freshwater runoff (7.66 Gt yr-1 decade-1) increases since the 1990s. Synthesized evidence from 94 marine biota time series showed 73 exhibiting significant changes, and 37 identified an environmental driver: sea ice (20), temperature (19), and runoff (2). Only four time series considered multiple drivers. Biota time series trends mirrored regional environmental changes; 78 % changed significantly in West, East and Southeast regions combined, 73 % in southwest, and 56 % in the northern regions. Fish, benthic flora, and benthic fauna responses remained unclear due to data gaps, underscoring the need for further research. In conclusion, our findings reveal widespread biological change linked to climate but with distinct regional patterns in environmental drivers and associated responses across Greenland.
