Recreational Diving and Hawksbill Sea Turtles (Eretmochelys imbricata) in a Marine Protected Area

Recreational diving is a form of ecotourism that is traditionally viewed as an ecologically sustainable activity prompting increased awareness for the marine environment. Recent studies, however, indicate that recreational diving may cause unintended behavioral changes in marine macrofauna. Few studies, however, have specifically investigated the effects of recreational diving on sea turtles. I conducted in-water observations and turtle sightings surveys from June 9 to August 21, 2014, in Roatán, Honduras, to determine if differences in dive site use and diver behavior alter the behavior of critically endangered hawksbill sea turtles (Eretmochelys imbricata) in a marine protected area (MPA). I found that hawksbill sightings distributions within the RMP did not vary with recreational diving pressure during an 82-day study period suggesting that turtle abundance within the RMP is independent of diving pressure. We found that turtles decreased the amount of time they spent eating, investigating, and breathing when approached by divers (1-4). Additionally, sightings studies indicated that divers in the RMP require additional training to accurately identify sea turtles species and record sightings data. Based on my findings, I made several recommendations to the Roatán Marine Park including the implementation of long-term sea turtle sightings and photo-identification surveys in the RMP, and suggested additional studies for other MPAs and researchers. Specifically I recommended that additional studies be conducted to compare recreational diver impacts on hawksbill sea turtle behavior within and outside MPAs, and measure seasonal variation in turtle sightings, dive site use, and foraging habitat in MPAs. As recreational diving continues to increase worldwide, it is imperative that management officials and researchers understand the impacts of recreational diving on sea turtle behavior, physiology, and population dynamics, in order to protect these important marine macrofauna. The current study provides the first data on the impacts of recreational diving on sea turtles. The results of this study will enable local management officials to implement effective regulations for diver and sea turtle interactions. Additional research building from the current study, should be conducted both in Honduras and globally, to further elucidate the impacts of recreational diving on different sea turtle species

Does Recreational Diving Alter Hawksbill Sea Turtle Foraging Behavior? Results from a Marine Protected Area, Honduras

Recent studies indicate that recreational diving may cause unintended behavioral changes in marine macrofauna. The hawksbill sea turtle (Eretmochelys imbricata) is a critically endangered species encountered by recreational divers in marine protected areas (MPAs) circumtropically. Few studies, however, have examined the impacts of recreational diving on sea turtle behavior. We conducted in-water observations of 61 juvenile hawksbill turtles from June 12 to September 2, 2014 in the Roatán Marine Park (RMP), Roatán, Honduras, to quantify the impacts of recreational diving on hawksbill behavior. We recorded turtle behaviors and the number of behavior bouts to test the effects of diver approach on sea turtle behavior. As a control for diver interactions, we began all observations by recording turtle behavior for approximately 3–5 m, and to test if diver approach affected a change in turtle behavior, we instructed different sized groups of divers (1-4) to slowly approach each turtle. We used the Interactive Individual Identification System (I3S): Pattern (Version 4.0.1) to test for repeat individuals. To test for associations between behavior bouts and behavior time we ran Spearman’s correlations. We also ran repeated measures ANCOVAs, comparing the total time turtles engaged in each behavior before and after divers approached turtles. Our results indicate that the amount of time turtles engage in eating, investigating, and breathing activity was correlated with the number of behavior bouts of each behavior. We also found that the amount of time turtles spent eating, investigating, and breathing decreased when approached by divers. Our results suggest diver habituation may negatively impact sea turtle behaviors, however it is unknown if recreational diving has a cumulative effect on turtle behavior over time. We recommend that MPA managers should implement monitoring programs that assess the impacts of tourism on sea turtles. We have established monitoring of hawksbills as representative species of marine habitats which have the potential to be heavily impacted by dive tourism, and provide recommendations for continued monitoring of the resource

Patterns of Habitat Use and Trophic Structure in Turtle Grass (Thalassia testudinum)-Dominated Systems Across the Northern Gulf of Mexico

Seagrass structural complexity is a primary driver of nekton recruitment and faunal community structure. Few studies, however, have quantified the role of seagrass complexity on habitat use and trophic structures over large spatial scales. A large-scale simultaneous survey was conducted to assess relationships of multiple seagrass morphological complexity metrics to nekton habitat use, trophic dynamics, and blue crab (Callinectes sapidus) growth and mortality across the Northern Gulf of Mexico. Seagrass morphological and nekton community characteristics depended on site and season, and regional variation in seagrass morphology was an important driver of juvenile nekton abundance, species richness, beta diversity, assemblage structure, and functional diversity across the Northern GOM. Results from a stable isotope survey indicate that food web structures across turtle grass (Thalassia testudinum)-dominated ecosystems are similar, although there was a clear trend of more depleted carbon isotopes in primary producers, fish, shrimp, and crabs at sites in the Eastern GOM and more enriched isotopes at sites in the Western GOM, which may be associated with site-specific differences in environmental conditions, such as freshwater inflow and nutrient inputs. Blue crab growth and mortality experiments revealed that growth and mortality rates varied across the six sites, but overall mortality rate declined with increasing seagrass leaf area index and crab size. Blue crab growth rates, however, had no measurable relationship with seagrass complexity metrics. Results from this work indicate that habitat complexity metrics such as shoot density, canopy height, and leaf area index are important factors that define the nursery functions of seagrass habitats and should be incorporated into monitoring programs, conservation initiatives, and fishery models. This study also demonstrates the utility of conducting large-scale comparative studies to reveal regional differences and similarities in trophic structures. Finally, this study highlights the need for additional regional and species-specific studies of environmental drivers of nekton community production throughout the GOM, and our results suggest that models of nekton production in seagrass habitats should be created at regional, as well as local, scales to identify broad patterns but also to account for site-specific differences in nekton responses to environmental and habitat characteristics

Effects of Reservoir Drawdown on Riffle Macroinvertebrate Communities

In 2007 Keystone Pond, a reservoir behind the Boardman dam, Boardman River, Grand Traverse County, Michigan, USA was drawn down in preparation for dam removal. The objective of this study was to quantify the effects of drawdown on benthic macroinvertebrate riffle communities by comparing a downstream site in a newly formed channel to an upstream control. Since 2008 a total of 2338 macroinvertebrates have been sampled and identified to the lowest practical taxonomic level. Data were analyzed using Chi-Square goodness of fit tests, Simpson\u27s Index of diversity, and Sørensens\u27 Quotient of Similarity. We found that macroinvertebrate communities in the new channel have recovered to a more natural condition and show increasing similarity to the upstream control site

Latent image diffraction from submicron photoresist gratings

Light scattering from latent images in photoresist is useful for lithographic tool characterization, process monitoring, and process control. In particular, closed‐loop control of lithographic processes is critical for high yield, low cost device manufacturing. In this work, we report use of pulsed laser diffraction from photoresist latent images in 0.24 μm pitch distributed feedback laser gratings. Gated detection of pulsed light scattering permits high spatial resolution probing using ultraviolet light without altering the latent image. A correlation between latent image and etched grating diffraction efficiencies is demonstrated and shows the value of "upstream" monitoring

Deciphering Lyman α\alpha blob 1 with deep MUSE observations

Context: Lyman $\alpha$ blobs (LABs) are large-scale radio-quiet Lyman $\alpha$ (Ly$\alpha$) nebula at high-$z$ that occur predominantly in overdense proto-cluster regions. Especially the prototypical SSA22a-LAB1 at $z=3.1$ has become an observational reference for LABs across the electromagnetic spectrum. Aims: We want to understand the powering mechanisms that drive the LAB to gain empirical insights into galaxy formation processes within a rare dense environment at high-$z$. Methods: LAB 1 was observed for 17.5h with the VLT/MUSE integral-field spectrograph. We produced optimally extracted narrow band images in Ly$\alpha$ $\lambda1216$ and HeII $\lambda1640$. By using a moment based analysis we mapped the kinematics of the blob. Results: We detect Ly$\alpha$ emission to surface-brightness limits of $10^{-19}$erg s$^{-1}$cm$^{-2}$arcsec$^{-2}$. At this depth we reveal a bridge between LAB 1 and its northern neighbour LAB 8, as well as a shell-like filament towards the south of LAB 1. We find a coherent large scale east-west $\sim$1000 km s$^{-1}$ velocity gradient that is aligned perpendicular to the major axis of the blob. We detect HeII emission in three distinct regions, but we can only provide upper limits for CIV. Conclusions: Various gas excitation mechanisms are at play in LAB 1: Ionising radiation and feedback effects dominate near the embedded galaxies, while Ly$\alpha$ scattering is contributing at larger distances. However, HeII/Ly$\alpha$ ratios combined with upper limits on CIV/Ly$\alpha$ can not discriminate between AGN ionisation and feedback driven shocks. The alignment of the angular momentum vector parallel to the morphological principal axis appears odds with the predicted norm for high-mass halos, but likely reflects that LAB\,1 resides at a node of multiple intersecting filaments of the cosmic web. (Abridged)Comment: Revised version. Accepted for publication in A&