**5. Ultraviolet radiation**

Ultraviolet light has a wavelength shorter than visible light and is named as such due to the emitted electromagnetic waves with frequencies above that of visible violet light. UVA and UVB wavelengths emitted by the sun affect animal behavior and physiology. UVA radiation is exploited by some pollinating insects to facilitate the detection of flower condition for nectar production in pollination. UVB radiation may affect reproduction and development as well as synthesis of vitamin D (Schaumburg et al., 2010). Overexposure to UVB is known to increase mutation rates in individual cells of whole organisms. The targets of UVB damage within living cells include nucleic acids, proteins, and lipids. Damage to these can inhibit DNA and cellular processes as well as impair cell membranes.

#### **5.1 Aquatic organisms**

Wavelength and intensity of solar radiation are modified as they travel through water but at shallow depths UV radiation is only able to penetrate a certain distance. Organisms found in epipelagic and littoral zones include phyto- and zooplankton, invertebrates, fish eggs and larvae, as well as entire ecosystems such as coral reefs. Some species of zooplankton change their vertical migration patterns within aquatic habitats to avoid exposure to UV radiation. Others respond by increasing pigmentation, an energetically costly process that can increase the organism's visibility to predators (Häder et al., 2007). The photochemical efficiency of some algae, such as those responsible for red tide, decreases when subjected to high solar radiation for short periods of time. However, if the algae are exposed to UV radiation for prolonged periods, they may be able to acclimate to this extended time by increasing protein repair and synthesizing UV-absorbing compounds (Guan et al., 2011). UV radiation induces decreased production of biomass such as phytoplankton, which can lead to a reduced capacity to sequester carbon dioxide, a gas that causes increased insolation of the Earth's atmosphere and is postulated as a major contributor to climate change (Hoffert & Caldeira, 2004).

Males of some pinniped species claim a territory rather than a harem and must rely on the habitat within their territory to entice or gain access to reproductive females. For example, South Australian fur seals exhibit several behavioral mechanisms to dissipate excess heat before finally abandoning their territory for access to water as TB approaches a certain thermal threshold often correlated with substrate (rock) temperature. Reproductive success of male New Zealand fur seals may depend on how much water is present within their territory. Males with areas including tide pools or along the shoreline have more access to females than males with no water in their territory. Male Northern fur seals that abandon their territories suffer a 50% reduction in mating success, whereas males of Southern Australian fur seal with no access to water average only 1.7 copulations per male compared to 3.6 copulations per male near a water source (Gentry, 1973). Southern sea lion males with territories lacking water access experience half the copulation frequencies of males with available water. During their forays to the water line, female Southern Australian fur seals expose themselves more frequently to males versus females that remain stationary and thus may contribute to an increased pregnancy rate

Ultraviolet light has a wavelength shorter than visible light and is named as such due to the emitted electromagnetic waves with frequencies above that of visible violet light. UVA and UVB wavelengths emitted by the sun affect animal behavior and physiology. UVA radiation is exploited by some pollinating insects to facilitate the detection of flower condition for nectar production in pollination. UVB radiation may affect reproduction and development as well as synthesis of vitamin D (Schaumburg et al., 2010). Overexposure to UVB is known to increase mutation rates in individual cells of whole organisms. The targets of UVB damage within living cells include nucleic acids, proteins, and lipids. Damage to these can

Wavelength and intensity of solar radiation are modified as they travel through water but at shallow depths UV radiation is only able to penetrate a certain distance. Organisms found in epipelagic and littoral zones include phyto- and zooplankton, invertebrates, fish eggs and larvae, as well as entire ecosystems such as coral reefs. Some species of zooplankton change their vertical migration patterns within aquatic habitats to avoid exposure to UV radiation. Others respond by increasing pigmentation, an energetically costly process that can increase the organism's visibility to predators (Häder et al., 2007). The photochemical efficiency of some algae, such as those responsible for red tide, decreases when subjected to high solar radiation for short periods of time. However, if the algae are exposed to UV radiation for prolonged periods, they may be able to acclimate to this extended time by increasing protein repair and synthesizing UV-absorbing compounds (Guan et al., 2011). UV radiation induces decreased production of biomass such as phytoplankton, which can lead to a reduced capacity to sequester carbon dioxide, a gas that causes increased insolation of the Earth's atmosphere and is postulated as a major contributor to climate change (Hoffert & Caldeira,

inhibit DNA and cellular processes as well as impair cell membranes.

(Campagna & Le Boeuf, 1998).

**5. Ultraviolet radiation** 

**5.1 Aquatic organisms** 

2004).

Although many ectotherms are able to use solar radiation as a heat source, ultraviolet radiation can have detrimental affects, especially on certain early development stages. In larval stages of some fish, UV radiation can affect development, increase mutation rates, or cause skin and ocular damage. When exposed to full solar UV radiation, yellow perch eggs actually perish before they hatch (Häder et al., 2007). Invertebrates such as sea urchins are also inhibited by UVB radiation at different life stages. In some species apoptosis or abnormal development occurs in the embryos, while adults of other species exhibit a covering behavior, using pieces of debris to block direct contact with solar rays penetrating through shallow water (Häder et al., 2007; Nahon et al., 2009). UVB radiation is known to decrease survivability of amphibian embryos or larvae depending on species (Häkkinen et al., 2001).

The mortality of coral reefs throughout the world has been well documented and is partly attributed to rising ocean temperatures, pollution, and UV radiation. Bleaching occurs at a thermal threshold and the coral dies soon after the photosynthetic energy producing zooxanthellae are expelled. Corals exposed to high levels of UV radiation receive damage to both the symbiotic zooxanthellae and the coral tissue (Lesser & Farrell, 2004). Pathways involving carbon fixation and photochemistry in the zooxanthellae along with DNA damage and necrosis of the host coral tissues are the results of thermal stress due to the high irradiance of solar radiation. The presence of high UV radiation can lower the bleaching threshold, decreasing the time it takes to bleach in an environment that may otherwise not be as stressed. However, some coral reef species are able to sequester substances acquired through their diet into UV-absorbing elements (Dunne & Brown, 2001).
