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Chemical pollutants, coastal zone destruction, habitat loss, nutrient discharges, hypoxic zones, algal blooms and catastrophic overfishing have all heavily impacted life in our oceans (Bowen and Depledge, 2006). Major efforts are being made worldwide to manage and minimise these threats. However, one particular pollutant, light, is still permitted to flood into our seas almost unchecked. It is alarming that as the intentional and unintentional illumination of the coastal zone and nearshore environment increases unabated, we still have little idea of the extent to which intertidal and sublittoral ecosystems are being affected. There is also growing concern regarding the introduction of light into the deep sea (Widder et al., 2005).
Light pollution in the sea
Chemical pollutants, coastal zone destruction, habitat loss,
nutrient discharges, hypoxic zones, algal blooms and catastrophic
overfishing have all heavily impacted life in our oceans (Bowen
and Depledge, 2006). Major efforts are being made worldwide to
manage and minimise these threats. However, one particular
pollutant, light, is still permitted to flood into our seas almost
unchecked. It is alarming that as the intentional and unintentional
illumination of the coastal zone and nearshore environment in-
creases unabated, we still have little idea of the extent to which
intertidal and sublittoral ecosystems are being affected. There is
also growing concern regarding the introduction of light into the
deep sea (Widder et al., 2005).
1. Sensitivity to light
Almost all living organisms are sensitive to changes in the qual-
ity and intensity of natural light in the environment (Longcore and
Rich, 2004). This is such a widely distributed characteristic that it
seems likely to have arisen very early in evolutionary history, pos-
sibly on several occasions. It might even suggest that the evolution
of life in the oceans proceeded largely in the photic zone. Obvi-
ously, for algae and seaweeds, photosynthetic activity is critically
dependent on available light, while in marine animals, tidal, daily,
monthly and seasonal cycles in natural light intensity and quality
are reflected in rhythmical fluctuations in behaviour and physiol-
ogy that are appropriately tuned to the prevailing ecological cir-
cumstances (Depledge, 1984).
Humans use the influence of light on several kinds of organisms
to great advantage. For example, for centuries fishermen have de-
ployed lanterns to attract fish to their nets, while modern day nat-
ural resource managers set out lights to attract larval fish to coral
reefs to boost fish stocks and enhance biodiversity (Munday et al.,
1998). There are numerous vivid accounts in the literature of peo-
ple using their knowledge of light-entrained rhythms to reap re-
wards. South Pacific islanders for example, exploit moon phase
spawning of polychaete worms to ensure bountiful harvests of
eggs and sperm that are considered a culinary delicacy (Thorson,
2. Light pollution
Light pollution of the sea has only become a really significant
issue over the last ca. 50–80 years. It has been defined as the
‘‘degradation of the photic habitat by artificial light” (Verheijhen,
1985). Simply put, light pollution occurs when organisms are ex-
posed to light in the wrong place, at the wrong time or at the
wrong intensity. Following the mounting, well-publicised evidence
of disturbance of the behaviour of birds, bats and insects, there is
now growing concern that light pollution might exert damaging ef-
fects on aquatic species in lakes, rivers and our seas, especially in
coastal areas. All organisms equipped with an optic orientation
system are potentially susceptible. In the sea, the behaviour, repro-
duction and survival of marine invertebrates, amphibians, fish and
birds have been shown to be influenced by artificial lights (Verheij-
hen, 1985). These effects arise from changes in orientation, disori-
entation, or misorientation and attraction or repulsion from altered
light environments (Longcore and Rich, 2004; Salmon et al., 1995).
In animals exhibiting compulsive stimulus behaviour, the strength
and number of artificial lights may override any feedback control
mechanisms. This is exemplified by sea turtles hatchlings that rely
on visual cues to orient themselves seaward, which consequently
renders them vulnerable to light pollution. In one anecdotal report,
500 green sea turtle hatchlings crawled to their deaths in an unat-
tended bonfire on a beach of Ascension Island (Mortimer, 1979).
On a Turkish beach, light pollution arising from a paper mill, a
tourist resort and a coastal village led to less than 40% of logger-
head turtle hatchlings reaching the surf (Peters and Verhoeven,
1994). The construction of buildings in close proximity to critically
important nesting beaches, as seen in the recent urban develop-
ment in Gabon’s capital, Libreville, places human populations and
their attendant light sources close to critical nesting sites for the
endangered leatherback sea turtle (Bourgeois et al., 2009). Disori-
entation and misorientation due to light pollution often divert
hatchlings along their paths to the sea leading to unnecessary en-
ergy expenditure and increased risks of dehydration and terrestrial
predation (Bourgeois et al., 2009; Verheijhen, 1985). Urban sky-
lines can present irregular silhouettes and as a result, unreliable
cues to female turtles. The confusing horizon field presented to
new hatchlings which rely heavily on horizon elevation cues re-
sults in increased mortality (Salmon, 2006). Indirect adverse effects
of artificial lighting include a higher risk of human interference via
greater likelihood of approach towards more visible animals and of
abandonment of nesting attempts if turtles become aware of hu-
mans prior to oviposition.
Other ecological effects of light pollution include disruption of
predator–prey relationships. For example, Harbor seals (Phoca vitu-
lina) congregate to feed in illuminated areas on juvenile salmon as
they migrated downstream. Predation falls off when the lights are
turned off (Yurk and Trites, 2000). In zooplankton, vertical migra-
tions in the water column with the day–night cycle help to reduce
predation by fish and other marine organisms, when light is avail-
able (Gliwicz, 1986). Artificial light disturbs this activity. Commu-
nity changes arising from light pollution may have knock on effects
for ecosystem functions (Gliwicz, 1986, 1999). Even remote areas
can still be exposed to sky glow. Along the expanding front of
suburbanization, light may spill into wetlands and estuaries that
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Marine Pollution Bulletin 60 (2010) 1383–1385
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are often the last open spaces in, or close to, cities (Longcore and
Rich, 2004).
Perhaps surprisingly, light pollution penetrates into deep ocean
environments (Kochevar, 1998). Here, only very dim, homochro-
matic, down light is available, supplemented by bioluminescence
from marine organisms. Most inhabitants possess highly special-
ized visual systems, which are incredibly sensitive to even minute
amounts of light. This renders these organisms extremely vulnera-
ble to damage associated with bright artificial lights of manned
and unmanned submersible vehicles (Kochevar, 1998). The current
efforts to deal with the oil well disaster in the Gulf of Mexico has
revealed the extent to which light pollution can occur in the deep
sea, albeit that the effects are secondary to the effects of oil pollu-
tion in this case.
There is a widely held, but incorrect belief that organisms living
in caves (whether under the sea or under land masses) do not come
into contact with light and are therefore insensitive to it. However,
as with deep sea creatures, many cave dwelling organisms are bio-
luminescent and are exquisitely sensitive to any ambient light and
light pollution. Most if not all, cave dwelling organisms and others
living remotely from daylight, evolved from organisms that at one
time dwelt in the light and hence retain vestiges of light sensing
3. Growing concerns regarding light pollution
Over the last ca. 150 years there has been an exponential in-
crease in the use of artificial light to illuminate the night. This
trend continues to this day. On land, street lights, lighting in office
buildings and homes, and floodlit sports facilities, industrial com-
plexes, etc., are the sources which inadvertently introduce light
into nature (RCEP, 2009). In coastal areas, where many of our major
cities such as Mumbai, Shanghai, Alexandria, Miami, New York City
and London are located, long stretches of the shoreline are strongly
illuminated. Indeed, light pollution of shallow seas has become a
global phenomenon (Elvidge et al., 1997). There are at least 3351
cities in the coastal zones around the world shedding light onto
beaches and into sublittoral areas. In Asia, 18 of the region’s 20
largest cities are located on the coast, on river banks or in deltas.
Even in Africa where the availability of electric lighting is some-
times limited, coastal light pollution is emitted from major cities
such as Abidjan, Accra, Algiers, Cape Town, Casablanca, Dakar,
Dar es Salaam, Djibouti, Durban, Freetown, Lagos, Luanda, Maputo,
Mombasa, Port Louis and Tunis (UN-HABITAT, 2009).
Our understanding of the polluting nature of artificial light is
emerging concurrently with an understanding of how patterns of
human development and economic globalization are intensifying
its impact. The UN estimates that the global population will in-
crease to a point where there are two and one half billion more hu-
man inhabitants than today (UNPOPIN). Inevitably, this growth
will be associated with further light pollution. The nature and scale
of growth provides an even louder clarion call for focus on the
environmental consequences of artificial light as well the need to
mitigate those consequences. The main conclusion to be drawn
from looking at the changing population dynamics over the next
generation is that virtually all of the two and half billion new citi-
zens of our World will live in small and medium sized cities within
emerging economies (Balk et al., 2008). Thus, while mega-cities
continue in their dominant position, more modest sized cities will
serve as the true future centres of growth. This means that artificial
light will not only continue to intensify with population growth,
but that the number of locations of high intensity light pollution
will also increase dramatically. Even in areas where total popula-
tion growth is low, such as in the OECD countries, analysis suggests
that the environmental influences of night light will continue to
spread. Consideration of data provided by the US National Geo-
physical Data Center (NOAA), reveals that total population growth
and the spatial patterns of human growth can be, and often are,
unrelated (Bowen et al., 2006; FAO, 2005). Migration to the coast,
so common in many parts of the world, and the ‘‘sprawl” of devel-
opment, present a challenge regardless of total population growth
While most of the future increase in artificial light will reside
with permanent resident populations, economic globalization will
also play a role. In 2009, the UN World Tourism Organization
(UNWTO) estimated that there were nearly 900 million interna-
tional tourist arrivals worldwide. The economic growth and devel-
opment pressure (very often coastal) of new supporting
infrastructure, driven by international tourism, cannot be ignored.
Indeed, touristic development may be a disproportionately impor-
tant driver of artificial light use simply because it tends to occur in
areas of enhanced natural beauty and environmental vulnerabil-
ity. In other words, wherever tourism increases, so too does light
Holiday visits to beaches vividly reveal the extent to which arti-
ficial lighting systems have been deployed along coastlines. More
systematic studies demonstrate the extent of the change that has
occurred. Innovative research using satellite imagery has tracked
the movement of populations over time. This is based on the prin-
ciple that wherever human population density increases it is
almost always associated with increased use of artificial light at
night. From a comparison of images taken at various times over
the past 50 years with present day images, it is clear that not only
has population density increased in many coastal areas around the
World, but this is associated with dramatic increases in light inten-
sity in the coastal zone.
4. What can be done?
From a mitigatory/regulatory perspective the above mentioned
patterns of human population change may provide vehicles to
more efficiently limit future environmental damage associated
with artificial light. If intensifying urbanization is effectively antic-
ipated and understood, it might be easier to coordinate regulatory
responses and technological efficiencies of scale. Thus, if most of
the future growth is geographically concentrated, the ability to
coordinate light pollution control measures could be enhanced.
The same might be said of touristic development. It provides a
commonality of activity that can be dealt with by a more concerted
and directed response.
In all other spheres of activity that result in artificial light
impacting marine life, there are clearly possibilities to regulate
light spillage into the sea. Whether from coastal developments or
fishing, or from oil and mining exploration or from cruise liners
and other merchant shipping activities, there are a wide range of
opportunities to regulate and thereby minimise potential adverse
effects of light pollution. Simply embedding the idea that in every-
thing we do, consideration needs to be given to minimising the
amount of light we release into the environment, would be a help-
ful step forward.
5. Summary
Whatever is done, it is first and foremost essential to recognize
the scale and scope of the potential problem in hand. It is almost
unimaginable that if we discovered a new pollutant today that
had pronounced effects on fundamental cellular processes, that af-
fected biological rhythms of cells, and that potentially affect photo-
synthesis, that we would not control or regulate its release into
natural ecosystems! Yet this is precisely what we do when we
allow light to spill into our seas, estuaries, rivers and lakes, as well
as into terrestrial ecosystems. The evidence is clear that the
1384 Editorial / Marine Pollution Bulletin 60 (2010) 1383–1385
feeding, reproductive and migratory behaviour of some species is
already affected. It seems timely therefore to reconsider our prof-
ligate use of light and to pay more attention to its biological effects.
If nothing else, more prudent use of artificial light would also re-
duced energy consumption and related greenhouse gas emissions,
surely a worthy goal in itself?
We gratefully acknowledge the support of the UK Government
Foreign and Commonwealth Office and of the Peninsula Founda-
tion, UK, for providing financial support to facilitate collaboration
among the authors.
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Michael H. Depledge
European Centre for Environment and Human Health,
Peninsula Medical School,
Universities of Exeter and Plymouth,
Truro, TR1 3HD, UK
E-mail address:
Céline A.J. Godard-Codding
Department of Environmental Toxicology,
The Institute of Environmental and Human Health,
Texas Tech University,
Lubbock, TX 79409, USA
Robert E. Bowen
Environmental, Coastal and Ocean Sciences,
University of Massachussetts,
Boston, MA, USA
Editorial / Marine Pollution Bulletin 60 (2010) 1383–1385 1385
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Artificial Light at Night (ALAN) alters cycles of day and night, potentially modifying species' behavior. We assessed whether exposure to ALAN influences decision-making (directional swimming) in an intertidal rockfish (Girella laevisifrons) from the Southeastern Pacific. Using a Y-maze, we examined if exposure to ALAN or natural day/night conditions for one week affected the number of visits and time spent in three Y-maze compartments: dark and lit arms ("safe" and "risky" conditions, respectively) and a neutral "non-decision" area. The results showed that fish maintained in natural day/night conditions visited and spent more time in the dark arm, regardless of size. Instead, fish exposed to ALAN visited and spent more time in the non-decision area and their response was size-dependent. Hence, prior ALAN exposure seemed to disorient or reduce the ability of rock fish to choose dark conditions, deemed the safest for small fish facing predators or other potential threats.
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“ Sorry! what did you say ?” Consider how easy it is to miss some conversation details when it is noisy.
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Light pollution is a pervasive global stressor to natural systems. However, due to the proximity of human activities along the coasts and open ocean, light is a pervasive yet commonly overlooked pollutant in many marine habitats. There is a well‐developed body of literature on the visual physiology, behaviour and ecology of many marine taxa, and a re‐evaluation of these data can help inform risks of light pollution to impact marine organisms and ecosystems. This paper identifies key knowledge gaps in the study of marine light pollution ecology and recommends research and management foci for future study. Most work on this pollutant has focused on terrestrial ecosystems and taxa, where experts have learned how anthropogenic light influences behaviour, reproduction cycles and population dynamics. However, light pollution bleeds far beyond the shores, affecting many sensitive ecosystems with light available at unnatural times with varied makeup, such as varying intensities or spectra. This review discusses the current understanding of light dynamics underwater, photoreceptive systems of marine taxa and the documented ecological impacts. This lends a critical basis of understanding for the many gaps in marine light pollution biology. For example, little is known about effects of light on broad groups of marine taxa such as cetaceans, ecosystem‐level effects, or interactive impacts of light and other anthropogenic stressors. Light is a key structuring factor of the marine environment and can therefore elicit immense downstream effects on marine organisms individually, at the population‐ or ecosystem‐level. Light pollution is an urgent concern for marine ecosystems because marine organisms have tight relationships with their natural light environment. As the world moves deeper into the Anthropocene, assessing and mitigating the risks of this pollutant to key environmental and economic marine systems is critical to maintaining a healthy ocean.
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Negatywne oddziaływanie sztucznego oświetlenia (Artificial Light at Night – ALAN) jest jedną z głównych, antropogenicznych przyczyn odpowie�dzialnych za bezpośrednią śmiertelność ptaków migrujących nocą. Do udokumentowanego, negatywnego wpływu ALAN na ptaki zaliczane są: efekt przyciągania i efekt dezorientacji. Efekt bariery z kolei jest przedmiotem badań, jednak brakuje jak dotąd jednoznacznego stwierdzenia na temat charakteru tego zjawiska. Większość badań wskazuje, że za efekt przyciągania, przyczyniający się do kolizji z różnymi konstrukcjami na lądzie i na morzu, odpowiedzialne jest oświetlenie o barwie niebieskiej i zielonej. Jednak czerwone i białe światło również wskazywane było w badaniach jako wywierające wpływ na przyciąganie ptaków. Z uwagi na te rozbieżności, konieczne są dalsze badania, w efekcie których będzie możliwe określenie, jaka barwa światła będzie najbezpieczniejsza dla ptaków. W chwili obecnej zasadne wydaje się rekomendowanie wykorzystania źródeł światła o barwach ciepłych (żółtej, bursztynowej) o temperaturze barwowej nieprzekraczającej 3000 K.
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The State of Nature Report organizes and presents spatial and temporal information on the threats to our ecosystems and the significant processes impacting both ecosystems and biodiversity. The report aims to provide a scientific basis for developing informed, sustainable management regimes for open landscapes and biodiversity in Israel. Trends and Threats Volume (2022) presents the current situation and changes occurring in recent decades in a number of selected disciplines with respect to the impact of humans on nature in Israel. Biodiversity Volume (to be published in 2023) will monitor the changes in flora and fauna in Israel. Chapter 1 – Land Use in Israel (land cover) – mapping and analysis of land use change and conversion in recent years: built-up land, transportation infrastructure, agriculture (plantations and field crops), disturbed areas (quarries, solar farms, and more), natural and artificial water bodies and other uses. Chapter 2 – Vegetation Cover and Formations in Israel – mapping and analysis of the state of Israel’s woody vegetation based on remote sensing data: the current situation and the changes which have occurred since 1985, presented by phytogeographic region and climate variables. Chapter 3 – Fire in Natural and Forested Landscapes in Israel – spatial and temporal mapping, as well as analysis of the frequency of fire events, in natural and forested landscapes in Israel in the last seven years, presented by vegetation formation categories and the corresponding agencies responsible for each area. Chapter 4 – Management and Protection of Natural and Forested Landscapes in Israel – mapping and analysis of the protection levels applied to natural and forested landscapes in Israel, in regards to the main land management agencies and changes in the degrees of protection applied in recent years. Chapter 5 – Continuity and Fragmentation of Open Landscapes in Israel – mapping and analysis of the continuity and fragmentation of Israel’s open landscapes. Chapter 6 – Light Pollution in Israel – Ecological and Spatial Aspects – definition of a threshold level of light pollution, mapping of the current situation and changes during the last decade, analysis of pollution levels in nature reserves and KKL-managed forests, as well as select regional examples. Chapter 7 – Climate Change and its Impact on Biodiversity – a review of climate change phenomena, global and local climate forecasts, along with widespread and expected impacts on flora and fauna.
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Coastal watersheds and nearshore marine areas are the most valuable and dynamic places on Earth. Human population growth is great in these regions, which are home to some of the most sensitive habitats in the world. Coastal areas provide more than half of the overall service value derived from the global environment (Costanza et al., 1997). Natural (e.g., hurricanes and tsunamis) and human pressures on this environment require it to constantly adjust. More than any other area, the global coast has defined the progress of human culture and continues to be a singular influence in how humans connect to the world around them. For these reasons and others, the global coast should be a central focus in the environmental management decisions of governments at all levels. However, increasingly, we have come to understand that allowing the degradation and broad-scale change in coastal systems has another consequence—our own health.
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A cycle of zooplankton density that fluctuated in phase with the moon was observed throughout 1982-1983 in Cahora Bassa Reservoir on the lower Zambezi, in southeastern Africa. Despite constant birth rates, densities of four cladoceran and two copepod species, as determined from vertically hauled plankton net samples taken every 2-6 d, fluctuated over one order of magnitude. The pattern followed by each species included an exponential increase in population density from the last quarter of the moon through the new moon and the first quarter, till the full moon, then a sudden decrease resulting in lowest numbers during the moon's last quarter. The cycle was shown to be induced by predation. Much higher death rates between the full moon and the last quarter were caused by the abundant Tanganyikan sardine Limnothrissa miodon. As seen from an examination of gut contents, sardines crop zooplankton most efficiently on nights when the full or nearly full moon rises after sunset, i.e., when zooplankton approach the surface during darkness and become suddenly vulnerable in the first light of the rising moon. After the last quarter, zooplankton density is low, the moon gives little light, the fish shift to alternate food resources, and zooplankton populations grow exponentially again. I suggest that the moon phase cycle in zooplankton is a global phenomenon, but, previously uninterpreted, has been seen only as distracting @'random@' variations in seasonal density patterns. I also suggest that similar prey-predator interactions might have been responsible for selecting for and fixing intrinsic monthly rhythms in behavior and physiology of animals with long life-spans.
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At several locations on an urban nesting beach, loggerhead hatchlings emerging from their nests did not orient toward the sea. The cause was city lighting which disrupted normal seafinding behavior. Observations and experiments were conducted to determine why females nested where hatchlings were exposed to illumination, and how hatchlings responded to local conditions. In some cases, females nested late at night after lights were turned off, but hatchlings emerged earlier in the evening when lights were on. In other cases, the beach was shadowed by buildings directly behind the nest, but was exposed to lights from gaps between adjacent buildings. In laboratory tests, "urban silhouettes" (mimicking buildings with light gaps) failed to provide adequate cues for hatchling orientation whereas natural silhouettes (those without light gaps) did. Adding a low light barrier (simulating a dune or dense vegetation) in front of the gaps improved orientation accuracy. The data show that hatchling orientation is a sensitive assay of beach lighting conditions, and that light barriers can make urban beaches safer for emerging hatchlings. At urban beaches where it may be impossible to shield all luminaires, light barriers may be an effective method for protecting turtles.
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During spring, harbor seals Phoca vitulina feed at night under two bridges spanning the Puntledge River in Courtenay, British Columbia, Canada. Posi- tioned parallel to one another, ventral side up, the seals form a feeding line across the river to intercept thou- sands of out-migrating salmonid smolts. During a 4- week observation period in the spring of 1996, we at- tempted to disrupt the seals' feeding patterns by (a) de- ploying a mechanical feeding barrier (cork line), (b) al- tering the lighting conditions (lights on a bridge were turned off), and (c) installing an acoustic harassment device. We found acoustic harassment to be the most effective feeding deterrent. Of the other two deterrents, turning off the bridge lights was more effective than deploying a cork line, which had little effect. Acoustic harassment devices appear to be the most effective, non- lethal means for protecting juvenile salmonids from har- bor seal predation in portions of the Puntledge River.
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Methods that enhance larval settlement are required to examine the importance of recruitment in the dynamics of coral reef fish populations. Although it is known that larval reef fishes are attracted to light, here we show for the first time that a light-attraction device positioned above patch reefs at Lizard Island (Great Barrier Reef) significantly increased the number of fish settling on the reefs below. The device was a modified light trap with a tube allowing the vertical movement of larvae from the trap to the reef. The number of species of settling fishes, and the abundance and diversity of immigrant fishes were also greater on the light-enhanced reefs. By comparison, the alternative technique of enhancing recruitment using surface buoys moored to reefs was unsuccessful. Further studies are now required to determine whether enhanced recruitment using light-attractors leads to a longer-term increase in population size, as opposed to temporarily concentrating juveniles on the reef.
The Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) has a unique capability to detect low levels of visible and near-infrared (VNIR) radiance at night. With the OLS 'VIS' band data, it is possible to detect clouds illuminated by moonlight, plus lights from cities, towns, industrial sites, gas flares, and ephemeral events such as fires and lightning illuminated clouds. This paper presents methods which have been developed for detecting and geolocating VNIR emission sources with nighttime DMSP-OLS data and the analysis of image time series to identify spatially stable emissions from cities, towns, and industrial sites. Results are presented for the United States.
1.1. Carcinus maenas (L.) were exposed to alternating 6-hr periods of submersion (seawater, 9–10°C) and aerial exposure (air, 13°C) for 8–10 days.2.2. Following transfer to non-tidal conditions cardiac and locomotor endogenous rhythms persisted for at least 7–8 days.3.3. When 0.05 mg l−1 mercuric sulphate was added to the non-tidal seawater system 12–30 hr after transfer of the crabs, endogenous rhythms were disrupted.4.4. Locomotor activity increased and mean heart rate rose from 32.1 ± 4.6 bpm prior to pollution, to 44.7 ± 8.9 bpm after pollution.5.5. Impedance cardiograph trace heights remained unchanged implying little, if any, change in heart stroke volume.6.6. Masking or ablation of endogenous rhythms persisted throughout the period of recording.7.7. The significance of the results is discussed with regard to the lives of crabs in situ.
Observations of animals in the deep ocean typically require the use of bright lights that can damage eyes and disrupt normal behaviors. Although the use of infrared light is an effective means of unobtrusive observation on land, it is far less effective in the ocean where long wavelength light is rapidly attenuated by seawater. Here we describe in situ observations of the behavior of the sablefish, Anoplopoma fimbria, around a baited site under different lighting conditions. Fish were observed with low-light-level imaging that had adequate sensitivity to compensate for the attenuation losses associated with the use of long wavelength light in water. ROV-based experiments compared the number of sablefish seen around bait, illuminated alternately with red vs. white light. Significantly more fish were seen under red light than white light with the average number of sablefish observed per 10 min viewing interval under red light being 38.9 (±18.5 SD) compared to 7.5 (±7.1 SD) under white light. Under both red and white light sablefish spent only brief periods in the illumination field (10.5 s [±8.7 SD] under red light and 6.6 s [±8.7 SD] under white light). It appeared that sablefish were responding to competing drives of attraction to the bait and avoidance of the lights and that the avoidance was greater for white light than for red light. Observations were also made with the newly developed deep-sea observatory, Eye-in-the-Sea, using long wavelength LED illumination. The onset of LED illumination did not generally produce a startle response from fish around the bait, and in some cases invoked no response at all. However, in the majority of cases the fish moved out of the circle of red-light illumination during the 7.5 s recording period, indicating that the light was detectable and aversive to these fish. This was true with both 660 and 680 nm LED illuminators. We conclude that while a sharper short-wavelength cutoff of the illumination source is required to achieve truly unobtrusive observation, red light is nonetheless significantly less disruptive than white light for observing deep-sea fish behavior, and can provide adequate illumination when used in combination with image-intensified cameras.
The coast of Gabon is one of the most important nesting sites for the endangered leatherback sea turtle Dermochelys coriacea. In this study, hatchling orientation was recorded during natural emergences at Pongara National Park, Gabon. This nesting beach is located close to both the capital of Gabon and a developing resort area, Pointe Denis. Under natural conditions most sea turtle hatchlings emerge at night and orient to the ocean by crawling away from dark, high silhouettes landward towards the bright, low seaward horizons. Artificial lights interfere with natural cues and disrupt hatchling orientation. The relative influence of artificial lights, logs and erosion were assessed on the nesting beach in Pongara National Park using a linear mixed model. We found that the attraction to artificial lights was higher than the effect of silhouette cues landward alone, but could be balanced by the simultaneous presence of the moon. Based upon these results, we recommend combining light management in the resort area to reduce the light pollution on the nesting beach and reinforcement of natural cues landward to minimize the effect of the remaining light pollution from the capital.