Distribution of modern dinocysts and pollen in the western Mediterranean Sea (Algerian margin and Gulf of Lion)

Coussin, V.; Penaud, Aurélie; Combourieu-Nebout, Nathalie; Peyron, Odile; Schmidt, Sabine; Zaragosi, Sébastien; Vernal, Anne de; Babonneau, Nathalie

doi:10.1016/j.marmicro.2022.102157

Cited by 5 publications

(2 citation statements)

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“…Temperature is often considered the most important factor controlling dinocyst distributions, also in the GoM Zonneveld et al, 2013). However, other environmental parameters may also be of major importance for the spatial distribution of dinocysts, as studies from the West African coast and the Mediterranean Sea reported nutrient levels and/or primary productivity as the main driver (Dale et al, 2002;Coussin et al, 2022). Similarly, a study on an Iberian estuary reported a strong inshore-offshore trend in the dinocyst distributions, with high chlorophyll a and sea surface nitrate concentrations inshore and high sea surface salinity and annual bottom oxygen saturation percentages further offshore (Iria et al, 2023).…”

Section: Pollen Taxamentioning

confidence: 99%

“…The use of this ratio as an indicator for terrestrial influence was justified by a study that showed a decrease in pollen vs. dinocyst ratio offshore from the St. Lawrence Estuary, coinciding with an increase in δ 13 C org , indicating the shift in organic matter source from terrestrial to marine along the transect (De Vernal et al, 1991). However, the use of a modern calibration dataset that tests these indices is still limited, especially in river-dominated coastal margins along a land-sea transect (Coussin et al, 2022;Iria et al, 2023). It is, therefore, important to understand the occurrence and spatial distribution of pollen and dinocysts in the modern environment.…”

Section: Introductionmentioning

confidence: 99%

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Dinoflagellate cyst and pollen assemblages as tracers for marine productivity and river input in the northern Gulf of Mexico

Yedema,

Donders,

Peterse

et al. 2023

J. Micropalaeontol.

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Abstract. Both marine dinoflagellate cysts and terrestrially derived pollen and spores are abundant in coastal sediments close to river mouths, making sediment records from such settings ideal to simultaneously study land–ocean climate interactions, marine productivity patterns and freshwater input over time. However, few studies consider the combined calibration of these palynological proxies in modern coastal sediments offshore from rivers, which is needed to strengthen the interpretation of paleoreconstructions. Here, we analyze the palynological content of marine surface sediments along land–sea transects off the Mississippi and Atchafalaya river mouths in the northern Gulf of Mexico (GoM) and test three palynological indices which are often employed in the paleo-domain: (i) the abundance of cysts of heterotrophic and autotrophic dinoflagellates (dinocysts) as a tracer for primary productivity (H/A ratio) and (ii) the ratio between non-bisaccate pollen and bisaccates (P/B) as well as (iii) the ratio between pollen (excluding bisaccates) and dinocysts (P/D), which are both tracers for river input and distance to the coast. Our results show that dinoflagellate cysts are most abundant on the shelf, where heterotrophic dinocyst species dominate coastal assemblages in reach of the river plume, while autotrophic taxa are more present in the oligotrophic open ocean. This is clearly reflected in decreasing H/A values further offshore. Individual dinocyst taxa also seem to inhabit specific niches along an onshore–offshore transect, linked to nutrient availability and proximity to the turbid river plume. The highest pollen concentrations are found close to the Mississippi river mouth and mostly represent a mixture of local coastal and upstream vegetation, whereas bisaccate pollen was most abundant further offshore of the Mississippi river. Multivariate redundancy analysis (RDA) performed on both pollen and dinocyst assemblages, a set of environmental parameters, and the three palynological ratios showed that net primary productivity was the most important variable influencing the dinocyst assemblages, likely as the result of nutrient input. Additionally, the RDA confirmed that the H/A ratio indeed seems to track primary productivity, while the P/B ratio results in a robust indicator for distance to the coast, and the P/D ratio better reflects river input. Together, our data confirm and further specify the suitability of these three palynological ratios in river-dominated coastal margins as proxies for (past) marine productivity and distance to the coast and river.

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