Tadzio Bervoets

Demographic changes in Pleistocene sea turtles were driven by past sea level fluctuations affecting feeding habitat availability

Abstract

Pleistocene environmental changes are generally assumed to have dramatically af-fected species’ demography via changes in habitat availability, but this is challenging to investigate due to our limited knowledge of how Pleistocene ecosystems changed through time. Here, we tracked changes in shallow marine habitat availability resulting from Pleistocene sea level fluctuations throughout the last glacial cycle (120–14  thou-sand years ago; kya) and assessed correlations with past changes in genetic diver-sity inferred from genome-wide SNPs, obtained via ddRAD sequencing, in Caribbean hawksbill turtles, which feed in coral reefs commonly found in shallow tropical waters. We found sea level regression resulted in an average 75% reduction in shallow ma-rine habitat availability during the last glacial cycle. Changes in shallow marine habitat availability correlated strongly with past changes in hawksbill turtle genetic diver-sity, which gradually declined to ~1/4th of present-day levels during the Last Glacial Maximum (LGM; 26–19   kya). Shallow marine habitat availability and genetic diver-sity rapidly increased after the LGM, signifying a population expansion in response to warming environmental conditions. Our results suggest a positive correlation be-tween Pleistocene environmental changes, habitat availability and species’ demog-raphy, and that demographic changes in hawksbill turtles were potentially driven by feeding habitat availability. However, we also identified challenges associated with disentangling  the  potential  environmental  drivers  of  past  demographic  changes, which highlights the need for integrative approaches. Our conclusions underline the role of habitat availability on species’ demography and biodiversity, and that the con-sequences of ongoing habitat loss should not be underestimated.

 

KEYWORDS: ddRAD sequencing, demographic change, habitat availability, Pleistocene sea turtles, sea level change

Date
2021
Data type
Scientific article
Theme
Education and outreach
Research and monitoring
Geographic location
Aruba
Bonaire
St. Eustatius
St. Maarten

Areal survey- Bait balls East Coast Bonaire

Aerial survey by the DCNA recording data and taking photos of almost 30 bait balls. Species observed include: skipjack tuna, various seabirds, species of shark, spinner dolphin and various individual Brydes whales feeding. 

For more information, contact research@DCNAnature.org

Date
2021
Data type
Raw data
Theme
Research and monitoring
Geographic location
Bonaire

Diet and growth of juvenile queen conch Lobatus gigas (Gastropoda: Strombidae) in native, mixed and invasive seagrass habitats

ABSTRACT: Juvenile queen conch are primarily associated with native seagrass such as Thalassia
testudinum in large parts of their range in the Caribbean and the southern Gulf of Mexico. Here,
a number of non-native seagrass species have been introduced including Halophila stipulacea,
which is natural to the Red Sea and the Indo-Pacific. In the Caribbean, H. stipulacea often creates
dense continuous mats with little or no sediment exposed, compared to native seagrass, which
grows much less dense. We examined the diet and growth of juvenile conch in both native, mixed,
and invasive seagrass beds using stable isotope analysis and an in situ growth enclosure experiment.
Organic material in the sediment (i.e. benthic diatoms and particulate organic matter) was
found to be the most important source of carbon and nitrogen for juvenile queen conch in all 3
habitats investigated, and there was a significantly higher probability of positive growth in the
native seagrass compared to the invasive seagrass. Due to the importance of the organic material
in the sediment as a source of nutrition for juvenile conch, limited access to the sediment in the
invasive seagrass can potentially cause inadequate nutritional conditions to sustain high growth
rates. Thus, it is likely that there is a negative effect on juvenile queen conch growth currently
inhabiting invasive seagrass beds, compared to native seagrass beds, when other potential
sources of nutrition are not available.

Date
2019
Data type
Media
Theme
Education and outreach
Research and monitoring
Geographic location
St. Eustatius
St. Maarten