Light Pollution Induces Increased Seabird Mortality

By Olivia Schuitema, SRC Intern

Light pollution has increased fiercely over the last century, resulting in mass fatality events in seabirds, one of the most endangered groups of birds (Rodríguez, 2017). This phenomenon, called “grounding,” happens when land-based artificial lights attract seabirds to the shore, causing them to crash into human-built structures such as buildings and fences (Rodríguez, 2017). Once on land, the disoriented birds (Troy, 2013) are vulnerable to predation, starvation, and vehicle collisions, leading to the mass-mortality events.

Figure 1

Composite image of continental U.S. at night, showing light pollution (NASA, 2016).

In reviewing current literature on the topic, data shows that twenty-four of the seabird species most likely to ground due to artificial lights are listed as “globally threatened” on the IUCN Red List (Rodríguez, 2017). A large number of the species affected are petrels and shearwaters (Figure 2). Juvenile individuals flying from the nest for the first time, or “fledglings,” make up 68%-99% of all grounding seabirds (Rodríguez, 2017). Seabird disorientation and the path where fledglings are drawn off course towards land are still uncertain (Troy, 2013), but scientists hypothesize the artificial lights drown out the natural light of the moon and stars.

Figure 2

Newell’s Shearwater, Puffinus newelli (Hawaii.gov).

Three strategies can be taken to prevent the loss of seabird life: avoidance, minimization, and rehabilitation (Rodríguez, 2017). Avoidance (avoiding practices that are known to cause fatalities) can be implemented in both new and current housing developments; new developments can refrain from installing light systems associated with groundings (Rodríguez, 2017), and current communities can remove or turn off lights that are not being used. Minimization reduces the duration and intensity of artificial light on seabird individuals (Rodríguez, 2017), and can be implemented in areas of overlap between humans and seabirds. Rehabilitation is also a method used to rescue grounded birds, where stranding teams and people of the public bring individuals to designated rescue stations. Here, the birds will undergo rehab until they are in “release condition.” However, not all birds survive grounding or rehabilitation efforts, but can be used as indicators of various marine environmental conditions (Rodríguez, 2017). Long-term scientific studies can also utilize seabird carcasses to address issues such as oil pollution (Stienen, 2017).

Figure 3

Seabird Rehabilitation Sanctuary in Ponce Inlet, Florida (Wikimedia Commons).

There is still little information known about seabird attraction to artificial lights. Scientists recommend researching the ecology and biology of vulnerable seabird populations and the effects of light intensity on grounded individuals (Rodríguez, 2017). New classes of lights that are useful for humans, but safe for seabirds can also be explored (Troy, 2013). Overall, seabirds are of great ecological importance and have ecotourism value that support many local economies. As light pollution increases, seabirds are continually at risk of grounding, leading to possible mass-mortality events.

Works Cited

Rodríguez, Airam, Holmes, Nick D., Ryan, Peter G., Wilson, Kerry‐Jayne, Faulquier, Lucie, Murillo, Yovana, . . . Corre, Matthieu Le. (2017). Seabird mortality induced by land‐based artificial lights. Conservation Biology, 31(5), 986-1001.

Stienen, Courtens, Van de Walle, Vanermen, & Verstraete. (2017). Long-term monitoring study of beached seabirds shows that chronic oil pollution in the southern North Sea has almost halted. Marine Pollution Bulletin, 115(1-2), 194-200.

Troy, J., Holmes, N., Veech, J., & Green, M. (2013). Using observed seabird fallout records to infer patterns of attraction to artificial light. Endangered Species Research, 22(3), 225-234.

A right whale pootree: classification trees of faecal hormones identify reproductive states in North Atlantic right whales (Eubalaena glacialis)

By Brenna Bales, SRC Intern

Faecal samples are a surprising wealth of information. One might think that the end product of digestion would not hold more information than simply what an animal has eaten, but in fact, animal excretions can give information about stress levels, sexual maturity, and physiological condition. In this analysis, 112 faecal samples of 81 individually identified North Atlantic right whales (NARW) (Eubalaena glacialis) were assayed for four hormone metabolites: cortisol (stress hormone), oestrogen (female sex hormone), testosterone (male sex hormone), and progesterone (female pregnancy hormone) (Corkeron et. al., 2017). The results were then used to classify each whale in a tree diagram, in one of the following categories: mature male (MM), immature male (IM), immature female (IF), pregnant female (Preg), lactating female (Lact), and resting female (mature, non-pregnant, non-lactating) (Rest) (Figure 1).

Figure 1

The constructed tree of known reproductive states of North Atlantic right whales (Eubalaena glacialis) (Corkeron et. al., 2017).

In order to confirm results, the hormonal identifications were compared with previously collected life-history data from the NARW Identification Database (Right Whale Consortium, 2012). The surveying efforts of these whales off the Eastern coast of North America extends back to 1986, with 80% of the population sighted each year (Hamilton et. al., 2007). This is key to confirming the results of a 13-year data set, and supplements the claims that NARWs are an ideal species for faecal analysis, due to the wealth of identification data. Furthermore, the consistent diet of the whales, minimal temperature variation in the study area, and the rapid collection of samples make this faecal hormone analysis possible.

Figure 2

A North Atlantic right whale and calf swim side by side. (source: http://www.noaanews.noaa.gov/stories2009/ images/whale_andcalf.jpg).

Cortisol hormone concentrations can also be used to identify stress levels in NARWs from anthropogenic impacts, similar to what has been done in killer whale (Orcinus orca) populations, relating boat traffic to stress (Ayres et. al., 2012). As environmental stressors continue to mount, wild, free-ranging marine animal populations are at risk. The confirmation of anthropogenic impact is essential, so appropriate conservation actions can be taken. In conclusion, this classification of sexual maturity is useful in estimating the proportion of breeding individuals in the NARW population, and hopefully can be used in future studies to assess the health and reproductive abilities of the population.

References
Ayres KL, Booth RK, Hempelmann JA, Koski KL, Emmons CK, Baird RW, Balcomb-Bartok K, Hanson MB, Ford MJ, Wasser SK (2012) Distinguishing the impacts of inadequate prey and vessel traffic on an endangered killer whale (Orcinus orca) population. PLoS One 7: e36842.

Hamilton PK, Knowlton AR, Marx MK (2007) Right whales tell their own stories: the photo-identification catalog. In SD Kraus, RM Rolland, eds, The Urban Whale: North Atlantic Right Whales at the Crossroads. Harvard University Press, Cambridge, MA, pp 75-104.

Right Whale Consortium (2012). North Atlantic Right Whale Consortium Identification and Sightings Databases 31 December 2012 (New England Aquarium, Boston, MA, USA).

The Importance of Deep-Water Coral on the Antarctic Continental Shelf

By Sianna Raquel Vacca, SRC Intern

Throughout history, both natural and man-made causes have resulted in long-lasting effects on the oceans. While most organic processes yield gradual change, the impact of human activity alters nature by prompting and accelerating otherwise irregular events (e.g. rapid ocean acidification, warming, habitat destruction), diminishing the oceans’ supply of pristine areas and ecosystems. A “pristine ecosystem” is defined as an area that has been either minimally affected or entirely untouched by human activity/influence. The depletion of these pristine areas impedes upon the ability to observe marine environments in their natural, undisturbed states. However, not all pristine marine habitats have been affected just yet.

Figure 1

Antarctic seafloor depicting an array of marine organisms including Antarctic scallops and brittle stars. Pixabay.

A study conducted by a group of scientists based in Barcelona, Spain recently explored the pristine populations of deep-water corals on the Antarctic continental shelf. Thanks to geographical factors, the practically desolate waters of the Antarctic have provided protection to these gorgonian species from human influence and this study, as one of the first of its’ kind, has contributed to filling several gaps regarding the population characteristics of this species. While little was known about their distribution, abundance, and demographics, ROVs (remotely operated vehicles) have proven that gorgonians play an important role in the creating the geographical structure of many Antarctic continental shelfs by adding a three-dimensional aspect to their habitat. The purpose of this study was to learn about and understand the ecological role of these corals, which can be used in conservation efforts.

The results showed that coral populations in Antarctic benthic environments were not only booming, but that their distribution gradually differed between the Northern and Southern regions of the Weddell Sea. They thrive at depths of 250-350m and despite such extreme conditions, gorgonian density is similar to coral population values in temperate and tropical ocean floors. This discredits the widely accepted belief that species richness proportionately decreases with increasing latitude. Hydrodynamic conditions are also favorable for gorgonians at these depths by accumulating particle suspension in the near-bottom water layers. These strong currents are advantageous by providing a constant food supply and keeping reefs clear of sediment.

While gorgonian populations proved to be overwhelmingly healthy in the Antarctic, they are exposed to certain environmental threats that a tropical reef would never face. Due to their slow growth rate and reproduction type, gorgonians are especially vulnerable to iceberg scouring. Iceberg scouring events occur when icebergs drift into shallow areas and come into contact with/scrape the seafloor as it moves along. Additionally, anthropogenic activities such as bottom-trawling and by-catch fishing result in large habitat destruction for these species. The authors of this study hope to bring awareness to the abundance and health of gorgonians, which can at least begin to protect them from human-related threats.

Figure 2

A diagram portraying iceberg scouring, the process by which icebergs scrape the seafloor as it drifts through the ocean. Iceberg scouring events pose a threat to gorgonian species on the Antarctic continental shelf because of their slow growth rate, reproduction type, and inability to quickly recover. Flickr.

References

Ambroso, Stefano, et al. “Pristine Populations of Habitat-Forming Gorgonian Species on the Antarctic Continental Shelf.” Scientific Reports, vol. 7, no. 1, 25 Sept. 2017, doi:10.1038/s41598-017-12427-y.

The effects of elevated temperature and ocean acidification on the metabolic pathways of notothenioid fish

By Abby Tinari, SRC intern

Notothenioid fish are typically found in the deep, cold waters of the Southern Ocean. Three species of fish native to the Ross Sea were studied to see how they may react to warmer and more acidic oceans.

Figure 1

(a) Pagothenia borchgrevunki (http://adam.antarcticanz.govt.nz), (b) Trematomus newnesi (http://adam.antarcticanz.govt.nz), (c) Trematomus bernacchii (Wikimedia Commons), (d) Ross Sea Location (Wikimedia Commons)

Methods

To measure the effects of temperature on the fish, individuals were randomly selected and placed in one of the four experimental treatment tanks. The experimental tanks consisted of a control treatment, a low temperature and high pCO2, high temperature and low pCO2, and high temperature and high pCO2 to test the individual and overall effects of temperature and pCO2 on the three-fish species. pCO2 is the partial pressure of carbon dioxide in the water. Each fish had an acclimation period that lasted anywhere from 7 to 56 days. Measurements of fish condition and growth were recorded over the course of the experiment. A few tests were performed to analyze enzymatic changes in the liver, white muscle tissue, and gills. One of the tests, the citrate synthase activity test measured how well the fish can release stored energy.

Results

T. bernacchii, the emerald codfish, was the only fish to display any significant impact from the treatments. The growth and condition declined significantly due to temperature but slowed as the acclimation period increased. The group of fish with the faster acclimation period had the largest decline of condition and growth, especially those that also had the multi-stress (high temperature and high <em>p</em>CO2) treatment. The temperature also influenced the Emerald Codfish’s oxygen consumption and metabolic rate. The high <em>p</em>CO2 tank had a small increase in metabolic rate. There were significant increases in citrate synthase activity, the first of which occurred after 7 days in the multi-stress treatment in the gills. By the 28-day acclimation, all treatments had significantly increased in both the liver and the gills.

The bald notothen, P. borchgrevinki, metabolic rates were significantly affected by temperature in the shorter acclimation periods. Interestingly, the oxygen consumption rates decreased in the high temperature treatments over time. Time and temperature were the main drivers in the citrate synthase activity increase in the gill tissues.

Metabolic rates in T. newnesi differed significantly between the acclimation groups with temperature as the main effect. No significant difference between pCO2 and temperature was present. There was however, an increased oxygen consumption rate after the 7 and 28-day acclimation period. The T. newnesi showed the least sensitivity to the treatments. The changes in Citrate synthase activity were not statistically significant.

Figure 2

Citrate synthase enzyme activity (±SE) of Trematomus bernacchii gill (A) and liver tissues (B), Pagothenia borchgrevinki gill (C) and liver tissues (D) and Trematomus newnesi gill (E) and liver tissues (F) acclimated at 7, 28 and 42 or 56 days to a control treatment (low temperature + low pCO2; black bars), low temperature + high pCO2 (white bars), high temperature + low pCO2 (dark gray bars) and high temperature + high pCO2 (light gray bars with cross hatches). Groups not connected by the same letter are significantly different from each other. (Enzor et al. 2017)

Discussion

This group of fish, the Notothenioid fish are critical to the Ross Sea food web. The three-species studied are consumed by seals, penguins, and other top predators. Studies like this one help to predict population responses for not only the Notothenioidei suborder but also other species which depend on these individuals for food.

Temperature had a greater adverse effect on the energy demands for two of the studied species. The fish may be able to acclimate to the higher temperatures, but only to an extent. Higher temperatures may mean a decreased ability to efficiently ingest food leading to decreased growth and other detrimental effects as seen in the Emerald codfish.

It should be noted that the long-term implications of the temperature and pCO2 on growth should be cautiously interpreted due to the small sample size and lack of growth even in the control samples.

References

Enzor LA, Hunter EM, Place SP (2017) The effects of elevated temperature and ocean acidification on the metabolic pathways of notothenioid fish. Conserv Physiol 5(1): cox019; oi:10.1093/conphys/cox019