Unrecognized loss of seagrass communities based on molluscan death assemblages: historic baseline shift in tropical Gulf of Aqaba, Red Sea

Gilad, Ehud; Kidwell, Susan M.; Benayahu, Yehuda; Edelman‐Furstenberg, Yael

doi:10.3354/meps12492

Cited by 16 publications

(12 citation statements)

References 36 publications

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“…The current in the GoA moves southwards on the western coast leading to a faster dilution of nutrients in the North Beach and at the same time accumulating a higher amount of nutrients in the South Beach ( Abelson et al, 1999 ). Moreover, biogeochemical differences in sediment characteristics (NB, muddy and dense; SB, sandy and loose) and different composition in sedimentary benthic faunal communities might have influenced nutrient dynamics at both sites ( Gilad et al, 2018 ). While we did not find any proof of nutrient enrichment in the water samples of the fertilized NB plots, we did, however, find that fertilized plots in the SB sites were significantly enriched in porewater P and N compounds as well as P in the water column, confirming that our fertilization was successful.…”

Section: Discussionmentioning

confidence: 99%

Nutrient History Affects the Response and Resilience of the Tropical Seagrass Halophila stipulacea to Further Enrichment in Its Native Habitat

et al. 2021

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Eutrophication is one of the main threats to seagrass meadows, but there is limited knowledge on the interactive effects of nutrients under a changing climate, particularly for tropical seagrass species. This study aimed to detect the onset of stress in the tropical seagrass, Halophila stipulacea, by investigating the effect of in situ nutrient addition during an unusually warm summer over a 6-month period. We measured a suite of different morphological and biochemical community metrics and individual plant traits from two different sites with contrasting levels of eutrophication history before and after in situ fertilization in the Gulf of Aqaba. Nutrient stress combined with summer temperatures that surpassed the threshold for optimal growth negatively affected seagrass plants from South Beach (SB), an oligotrophic marine protected area, while H. stipulacea populations from North Beach (NB), a eutrophic and anthropogenically impacted area, benefited from the additional nutrient input. Lower aboveground (AG) and belowground (BG) biomass, reduced Leaf Area Index (LAI), smaller internodal distances, high sexual reproductive effort and the increasing occurrence of apical shoots in seagrasses from SB sites indicated that the plants were under stress and not growing under optimal conditions. Moreover, AG and BG biomass and internodal distances decreased further with the addition of fertilizer in SB sites. Results presented here highlight the fact that H. stipulacea is one of the most tolerant and plastic seagrass species. Our study further demonstrates that the effects of fertilization differ significantly between meadows that are growing exposed to different levels of anthropogenic pressures. Thus, the meadow’s “history” affects it resilience and response to further stress. Our results suggest that monitoring efforts on H. stipulacea populations in its native range should focus especially on carbohydrate reserves in leaves and rhizomes, LAI, internodal length and percentage of apical shoots as suitable warning indicators for nutrient stress in this seagrass species to minimize future impacts on these valuable ecosystems.

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Section: Discussionmentioning

confidence: 99%

Nutrient History Affects the Response and Resilience of the Tropical Seagrass Halophila stipulacea to Further Enrichment in Its Native Habitat

et al. 2021

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“…Major losses in the extent of oyster reefs and scallop grounds, and reductions in the diversity of molluscan communities over the past decades and centuries were documented worldwide in marine siliciclastic environments (Edgar & Samson, ; Poirier et al ., ; Wilberg et al ., ; Thurstan et al ., ; Alleway & Connell, ; Martinelli et al ., ; Rick et al ., ). However, changes in carbonate production before and after major anthropogenic impacts in temperate carbonate environments remain less explored than in the tropics (Perry et al ., ; Cramer et al ., ; Albano et al ., ; Smith et al ., ; Gilad et al ., ). Ecological and palaeoecological analyses performed in the northern Adriatic Sea detected that the composition of benthic communities inhabiting siliciclastic muds changed towards the dominance of opportunistic species during the 20th century (Crema et al ., ; Barmawidjaja et al ., ; Gallmetzer et al ., ; Tomašových et al ., ).…”

Section: Introductionmentioning

confidence: 97%

A decline in molluscan carbonate production driven by the loss of vegetated habitats encoded in the Holocene sedimentary record of the Gulf of Trieste

et al. 2018

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Carbonate sediments in non‐vegetated habitats on the north‐east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand‐dwelling Gouldia minima and opportunistic Corbula gibba are time‐averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co‐occurring Gouldia minima . This age difference is driven by temporally disjunct production of two species coupled with decimetre‐scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top‐core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft‐bottom vegetated zones and hard‐bottom Arca beds) and present‐day oligophotic communities with organic‐loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats.

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“…Dietl and Smith, 2017; Kidwell, 2007; Kowalewski et al, 2000, 2015; Tomašových and Kidwell, 2017) and other environmental impacts (e.g. Albano et al, 2016; Bizjack et al, 2017; Gilad et al, 2018; Korpanty and Kelley, 2014; Tweitmann and Dietl, 2018).…”

Section: Introductionmentioning

confidence: 99%

Holocene fish assemblages provide baseline data for the rapidly changing eastern Mediterranean

Agiadi

Albano

2020

The Holocene

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The eastern Mediterranean marine ecosystem is undergoing massive modification due to biological invasions, overfishing, habitat deterioration, and climate warming. Our ability to quantify these changes is severely hindered by the lack of an appropriate baseline; most ecological datasets date back a few decades only and show already strong signatures of impact. Surficial death assemblages (DAs) offer an alternative data source that provides baseline information on community structure and composition. In this study, we reconstruct the marine fish fauna of the southern shallow Israeli shelf before the opening of the Suez Canal based on fish otoliths. We quantify the age of the otolith DAs by radiocarbon dating, and describe its taxonomic composition, geographic affinity, and trophic structure. Additionally, we test by radiocarbon dating the hypothesis that Bregmaceros, a presumed Lessepsian invader with continuous presence in the Mediterranean throughout the late Cenozoic, is a relict species. The otolith DA dates back to the mid-Holocene because 75% of the dated otoliths of the native species are older than the opening of the Suez Canal in 1869, suggesting that the DA is a proper baseline for quantifying modern impacts. Consistently, 97% of the otoliths and 88% of the species we collected belong to native Mediterranean species. The native anchovy Engraulis encrasicolus dominates the DAs, although gobiids are the most diverse group (14 species, 28%). The DAs show similar trophic structure to present-day pristine Mediterranean coastal fish assemblages. Two non-indigenous species are recorded here for the first time in the Mediterranean Sea, Amblygobius albimaculatus and Callogobius sp., highlighting the importance of DAs for detecting non-indigenous species. Finally, Bregmaceros otoliths are modern, not supporting the previous hypothesis that the taxon is a Pleistocene relict.

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Unrecognized loss of seagrass communities based on molluscan death assemblages: historic baseline shift in tropical Gulf of Aqaba, Red Sea

Cited by 16 publications

References 36 publications

Nutrient History Affects the Response and Resilience of the Tropical Seagrass Halophila stipulacea to Further Enrichment in Its Native Habitat

Nutrient History Affects the Response and Resilience of the Tropical Seagrass Halophila stipulacea to Further Enrichment in Its Native Habitat

A decline in molluscan carbonate production driven by the loss of vegetated habitats encoded in the Holocene sedimentary record of the Gulf of Trieste

Holocene fish assemblages provide baseline data for the rapidly changing eastern Mediterranean

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