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HIPPO environmental monitoring

HIPPO environmental monitoring:

Impact of phytoplankton dynamics on water column chemistry and the sclerochronology of the king scallop (Pecten maximus) as a biogenic archive for past primary production reconstructions

 

Abstract

As part of the HIPPO project (HIgh-resolution Primary Production multi-prOxy archives), environmental monitoring was carried out between March and October 2021 in the Bay of Brest. The aim of this survey was to better understand the processes which drive the incorporation of chemical elements into scallop shells and their links with phytoplankton dynamics. For this purpose, biological samples (scallops and phytoplankton) as well as water samples were collected in order to analyze various environmental parameters (element chemical properties, nutrients, chlorophyll a, etc.). Given the large number of parameters that were measured, only the major results are presented and discussed here. However, the whole dataset, which has been made available, is much larger and can potentially be very useful for other scientists performing sclerochronological investigations, studying biogeochemical cycles or conducting various ecological research projects. The dataset is available online.

 

Figure 10:Average Ba/Ca signals measured in shells of P. maximus that were collected from the sediment surface (blue curve, n=3) and 1 m above the substrate (red curve, n=3). The abundances of Chaetoceros spp. (dark green areas) and L. danicus (light green areas) are also shown.

 

Conclusions

In this article, only an overview of the results gathered during the HIPPO monitoring conducted at Lanvéoc during 2021 is presented. The dataset helps in better understanding the links between phytoplankton dynamics, water column chemistry and the incorporation of trace elements into the shells of P. maximus. However, the dataset also contains information useful for other topics of interest. Tables 1 and 2 compile all variables that have been made available for other scientists on the SEANOE platform (https://doi.org/10.17882/92043 – Siebert et al., 2023). Moreover, the hypotheses and assumptions given in this paper, as well as other topics that have not been mentioned, will be the focus of several articles that are currently in preparation.

 

Référence

Siebert, V., Moriceau, B., Fröhlich, L., Schöne, B. R., Amice, E., Beker, B., Bihannic, K., Bihannic, I., Delebecq, G., Devesa, J., Gallinari, M., Germain, Y., Grossteffan, É., Jochum, K. P., Le Bec, T., Le Goff, M., Liorzou, C., Leynaert, A., Marec, C., Picheral, M., Rimmelin-Maury, P., Rouget, M.-L., Waeles, M., and Thébault, J.: HIPPO environmental monitoring: impact of phytoplankton dynamics on water column chemistry and the sclerochronology of the king scallop (Pecten maximus) as a biogenic archive for past primary production reconstructions, Earth Syst. Sci. Data, 15, 3263–3281, https://doi.org/10.5194/essd-15-3263-2023, 2023.
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Mercury isotope clocks predict coastal residency and migration timing of hammerhead sharks

Abstract and highlights

  1. The management of migratory taxa relies on the knowledge of their movements. Among them, ontogenetic habitat shift, from nurseries to adult habitats, is a behavioural trait shared across marine taxa allowing resource partitioning between life stages and reducing predation risk. As this movement is consistent over time, characterizing its timing is critical to implement efficient management plans, notably in coastal areas to mitigate the impact of fisheries on juvenile stocks.
  2. In the Mexican Pacific, habitat use of the smooth hammerhead shark (Sphyrna zygaena) is poorly described, while the species is heavily harvested. Given the large uncertainties associated with the timing of out-migration from coastal nursery grounds to offshore waters prior to reproductive maturity, a more precise assessment of smooth hammerhead shark movements is needed.
  3. Photochemical degradation of mercury imparts mass-independent isotope fractionation (Δ199Hg) which can be used to discriminate between neonate coastal shallow habitats and the offshore deep foraging patterns of late juveniles. Here, we present the application of muscle Δ199Hg as molecular clocks to predict the timing of ontogenetic habitat shifts by smooth hammerhead sharks, based on their isotopic compositions at the initial and arrival habitats and on muscle isotopic turnover rate.
  4. We observed decreases in Δ199Hg values with shark body length, reflecting increasing reliance on offshore mesopelagic prey with age. Coastal residency estimates indicated that smooth hammerhead sharks utilize coastal resources for 2 years prior to offshore migration, suggesting a prolonged residency in these ecosystems.
  5. Policy implications. This study demonstrates how mercury stable isotopes and isotopic clocks can be implemented as a complementary tool for stock management by predicting the timing of animal migration—a key aspect in the conservation of marine taxa. In the Mexican Pacific, fishing pressure on shark species occurs in coastal habitats depleting juvenile stocks. Consequently, management decision support tools are imperative for effectively maintaining early life stage population levels over time. The finding that smooth hammerhead sharks extensively rely on highly fished habitats for 2 years after parturition supports the relevance of establishing a size limit in coastal fisheries and demonstrates how the current temporal shark fishing closure could lack efficiency for the species.

Graphical abstract.

 

Reference

Besnard, L., Lucca, B. M., Shipley, O. N., Le Croizier, G., Martínez-Rincón, R. O., Sonke, J. E., Point, D., Galván-Magaña, F., Kraffe, E., Kwon, S. Y., & Schaal, G. (2023). Mercury isotope clocks predict coastal residency and migration timing of hammerhead sharks. Journal of Applied Ecology, 60, 803–813. https://doi.org/10.1111/1365-2664.1438

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Marine invertebrates and noise

Abstract

Within the set of risk factors that compromise the conservation of marine biodiversity, one of the least understood concerns is the noise produced by human operations at sea and from land. Many aspects of how noise and other forms of energy may impact the natural balance of the oceans are still unstudied. Substantial attention has been devoted in the last decades to determine the sensitivity to noise of marine mammals—especially cetaceans and pinnipeds—and fish because they are known to possess hearing organs. Recent studies have revealed that a wide diversity of invertebrates are also sensitive to sounds, especially via sensory organs whose original function is to allow maintaining equilibrium in the water column and to sense gravity. Marine invertebrates not only represent the largest proportion of marine biomass and are indicators of ocean health but many species also have important socio-economic values. This review presents the current scientific knowledge on invertebrate bioacoustics (sound production, reception, sensitivity), as well as on how marine invertebrates are affected by anthropogenic noises. It also critically revisits the literature to identify gaps that will frame future research investigating the tolerance to noise of marine ecosystems.


Figure 4 : Marine Invertebrate sound sensory systems.

Highlights

(1) We reported on the current scientific knowledge on marine invertebrate bioacoustics (detection and production of sound) and their responses (physical, physiological and behavioural effects) to anthropogenic noise at different life stages, population and ecosystem levels. Although the impact of noise pollution in marine invertebrates is understudied, an exhaustive and systematic revision of literature provided evidence that anthropogenic noise is detrimental not only to these species but also to the natural ecosystems they inhabit.

(2) Considering that the effects of noise can be elicited from cellular to ecosystems level, the understanding of noise impact requires an interdisciplinary expertise to embrace a holistic vision of the problem.

(3) Further research must include a detailed protocol that would ideally provide not only accurate acoustic metrics and methods, but also long-term experiments, cumulative effects, gradients of noise exposure, potential recovery from chronic noise in a variety of taxonomic groups and noise sources.

(4) Multiple stressors effects have to be considered when assessing potential impacts of noise exposure.

(5) This review represents a valuable reference to provides guidance to natural resource managers when evaluating anthropogenic noise effects and developing future operations at temporal and spatial scales that are relevant to oceanic ecosystems.

 

Reference

Sole´ M, Kaifu K, Mooney TA, Nedelec SL, Olivier F, Radford AN, Vazzana M, Wale MA, Semmens JM, Simpson SD, Buscaino G, Hawkins A, Aguilar de Soto N, Akamatsu T, Chauvaud L, Day RD, Fitzgibbon Q, McCauley RD and Andre´ M. (2023) Marine invertebrates and noise. Front. Mar. Sci. 10:1129057. doi: 10.3389/fmars.2023.1129057

Read the paper

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The unaccounted dissolved iron (II) sink: Insights from dFe(II) concentrations in the deep Atlantic Ocean

Abstract

Hydrothermal vent sites found along mid-ocean ridges are sources of numerous reduced chemical species and trace elements. To establish dissolved iron (II) (dFe(II)) variability along the Mid Atlantic Ridge (between 39.5°N and 26°N), dFe(II) concentrations were measured above six hydrothermal vent sites, as well as at stations with no active hydrothermal activity. The dFe(II) concentrations ranged from 0.00 to 0.12 nmol L−1 (detection limit = 0.02 ± 0.02 nmol L−1) in non-hydrothermally affected regions to values as high as 12.8 nmol L−1 within hydrothermal plumes. Iron (II) in seawater is oxidised over a period of minutes to hours, which is on average two times faster than the time required to collect the sample from the deep ocean and its analysis in the onboard laboratory. A multiparametric equation was used to estimate the original dFe(II) concentration in the deep ocean. The in-situ temperature, pH, salinity and delay between sample collection and its analysis were considered. The results showed that dFe(II) plays a more significant role in the iron pool than previously accounted for, constituting a fraction >20 % of the dissolved iron pool, in contrast to <10 % of the iron pool formerly reported. This discrepancy is caused by Fe(II) loss during sampling when between 35 and 90 % of the dFe(II) gets oxidised. In-situ dFe(II) concentrations are therefore significantly higher than values reported in sedimentary and hydrothermal settings where Fe is added to the ocean in its reduced form. Consequently, the high dynamism of dFe(II) in hydrothermal environments masks the magnitude of dFe(II) sourced within the deep ocean.

Highlights

  • Considering oxidation, open ocean iron (II) concentrations are below 0.2 nmol L−1.
  • The highest measured iron (II) concentration was 69.6 nmol L−1 at the Rainbow vent.
  • In the open ocean iron (II) account for 20 % of the dissolved iron pool.
  • Oxygen variations within OMZ account for 60 % of iron(II) oxidation variability.

Reference

Gonzalez-Santana, D.; Lough, A. J. M.; Planquette, H.; Sarthou, G.; Tagliabue, A.; Lohan, M. C. The Unaccounted Dissolved Iron (II) Sink: Insights from DFe(II) Concentrations in the Deep Atlantic Ocean. Sci. Total Environ. 2023, 862, 161179.

https://doi.org/10.1016/j.scitotenv.2022.161179.

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Spatial distribution of tropical fish assemblages

Sea bottom

Comprehensive spatial distribution of tropical fish assemblages from multifrequency acoustics and video fulfils the island mass effect framework.

Describing fish distribution and associated environmental features is the first step toward understanding how fish communities are spatially structured and is a necessary step to conduct Marine Spatial Planning (MSP) and operate relevant protection policies.

Abstract

Tropical marine ecosystems are highly biodiverse and provide resources for small-scale fisheries and tourism. However, precise information on fish spatial distribution is lacking, which limits our ability to reconcile exploitation and conservation. We combined acoustics to video observations to provide a comprehensive description of fish distribution in a typical tropical environment, the Fernando de Noronha Archipelago (FNA) off Northeast Brazil. We identified and classified all acoustic echoes into ten fish assemblage and two triggerfish species. This opened up the possibility to relate the different spatial patterns to a series of environmental factors and the level of protection. We provide the first biomass estimation of the black triggerfish Melichthys niger, a key tropical player. By comparing the effects of euphotic and mesophotic reefs we show that more than the depth, the most important feature is the topography with the shelf-break as the most important hotspot. We also complete the portrait of the island mass effect revealing a clear spatial dissymmetry regarding fish distribution. Indeed, while primary productivity is higher downstream, fish concentrate upstream. The comprehensive fish distribution provided by our approach is directly usable to implement scientific-grounded Marine Spatial Planning..

Synthetic representation of the island mass effect as illustrated by the case of Fernando de Noronha.

Synthetic representation of the island mass effect as illustrated by the case of Fernando de Noronha.

Reference

Salvetat, J., Bez, N., Habasque, J., Lebourges-Dhaussy, A., Lopes, C., Roudaut, G., Simier, M., Travassos, P., Vargas, G., and Bertrand, A. 2022. Comprehensive spatial distribution of tropical fish assemblages from multifrequency acoustics and video fulfils the island mass effect framework. Scientific Reports 12(1): 8787. Nature Portfolio, Berlin. doi:10.1038/s41598-022-12409-9.
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