//
you're reading...

Book Review

As the Caribbean sand heats up female sea turtles rule the beach

The paper:

Laloë, J.-O., Esteban, N., Berkel, J., & Hays, G. C. (2016). Sand temperatures for nesting sea turtles in the Caribbean: Implications for hatchling sex ratios in the face of climate change. Journal of Experimental Marine Biology and Ecology, 474, 92–99. doi:10.1016/j.jembe.2015.09.015

Introduction

Sea turtles are some of the most charismatic sea creatures; even marine mammals and invertebrate enthusiasts can’t help but be curious about these fascinating reptiles. Unfortunately, six out of seven species of sea turtle are labeled vulnerable or critically endangered. Climate change threatens to disrupt sea turtle populations further in a variety of ways by changing movement patterns and egg hatching success.

Many species will suffer by climate change induced changes to habitat, but sea turtles have an added layer of complexity due to their typical reptile characteristic of temperature-dependent sex determination. This means that the temperature of the eggs determines if the adorable baby turtles will be male or female (higher temperature leads to more females). For a species that is in decline, an unnatural skew of the sexes could spell disaster. Because sea turtles climb onto beaches to lay eggs in the sand, as average sand temperature rises with climate, the sex of embryos may change.

 Fig. 1. Location of St. Eustatius in the Lesser Antilles in the north-eastern Caribbean. The study site, Zeelandia beach, is located on the eastern coast of St. Eustatius.

Fig. 1. Location of St. Eustatius in the Lesser Antilles in the north-eastern Caribbean. The study site, Zeelandia beach, is located on the eastern coast of St. Eustatius.

Motivated by sea turtle conservation, the researchers set out to quantify how warming temperatures will impact the sex ratio of future generations of turtles. The study focused on the green (Chelonia mydas), hawksbill (Eretmochelys imbricata), and leatherback (Dermochelys coriacea) sea turtles nesting in the North East Caribbean.

Methods

Field data used for this paper came from a turtle monitoring program active since 2002 on the island of St. Eustatius (Figure 1). Historical environmental variables were used including rainfall, tide, air temperature, and sea temperature. Projections of temperature change came from the United Nations Development Programme (UNDP).

Loggers were buried at depths to imitate nest placement each species of sea turtle, and recorded sand temperature hourly. Based on previous literature, a temperature of 29° C was chosen as the tipping point at which an egg will develop into a male or female.

Results and Significance

Sand temperature showed seasonal variation, unsurprisingly increasing over the spring and summer to peak in July, August, and September. The greater depths consistently showed lower temperatures with the greatest range in the hottest months. There was a strong relationship between higher air temperatures and higher sand temperatures, implying air temperature can be used to predict the change in temperature that buried eggs may experience (Fig 2.).

Mean temperature was higher than 29° C for every month of the nesting season. Historical sex ratios were estimated based on the temperature data. During the hottest part of the year, females made up over 90% of the nests, compared to 40% in February (Figure 3). Projecting the model into the future showed the incubation temperature of sea turtle nests will increase with means well over the sex determination threshold over the next 50 years.

Projection of incubation temperatures for Zeelandia beach. A projected increase of air temperatures at the study site will result in an increase of incubation temperatures. Predicted incubation temperatures were estimated for 1000 nests in 2030 (A), 2060 (B), and 2090 (C).

Fig 2. Projection of incubation temperatures for Zeelandia beach. A projected increase of air temperatures at the study site will result in an increase of incubation temperatures. Predicted incubation temperatures were estimated for 1000 nests in 2030 (A), 2060 (B), and 2090 (C).

turtle3

Fig 3. (A) Seasonality of incubation temperatures at Zeelandia beach and (B) resulting sex ratios. Historical (1823–2014) air temperatures were used to reconstruct the mean monthly incubation temperatures across this 90-year period. The horizontal lines define the 2012 nesting seasons for each of the three turtle species nesting on St. Eustatius: greens (dotted line), hawksbills (dashed line), and leatherbacks (solid line).

 

 

 

 

 

 

 

 

 

 

 

 

 

Though this nesting site (and sea turtle populations at large) historically shows a female bias in summer, the increase in sand temperature will push the sex ratio towards favoring females. To a certain extent, more females can be adaptive; males mate with multiple females, and females only need to mate once to produce multiple nests. However, as temperatures rise and stay higher for longer parts of the year, the bias toward an excess of females may not be sustainable. Studies such as this one show the importance of protecting nesting habitats, and perhaps particularly ones in colder climates with a tendency toward more males.

Discussion

Trackbacks/Pingbacks

  1. […] interesting work has been doing on sea turtle nests, some of which has been covered on Oceanbites. Did you know warm nests produce more females? Or that rising sea levels hinder hatching success? [Flickr – Jeroen […]

Post a Comment

Instagram

  • by oceanbites 2 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 3 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 4 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 5 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 5 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 7 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 8 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 9 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 9 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 9 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 10 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 11 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 11 months ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com