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Larval Sensory Systems
Although a pelagic larval stage allows many species to increase their dispersal range and decreases the risk of inbreeding, it comes with challenges. Without advanced sensory abilities, larvae are at risk of being washed away without suitable habitat for settlement. Marine larvae have evolved the ability to use a variety of sensory systems at different scales.

Magnetic Fields
Far from shore, larvae are able to use magnetic fields to orient themselves towards the coast over large spatial scales. There is additional evidence that species can recognize anomalies in the magnetic field to return to the same location multiple times throughout their life. Though the mechanisms that these species use is poorly understood, it appears that magnetic fields play an important role in larval orientation offshore, where other cues such as sound and chemicals may be difficult to detect.

Vision
Phototaxis (ability to differentiate between light and dark areas) is important for the detection of suitable habitat. The ability to perform phototaxis evolved relatively quickly and taxa that lack developed eyes, such as schyphozoans, use phototaxis to find shaded areas to settle away from predators.

Species that produce more complex larvae, such as fish, are able to use full vision to find suitable habitat on small spatial scales. Studies of damselfish have shown that larvae use vision to locate and settle near adults of the same species.

Sound
Marine larvae use sound and vibrations as a method of locating suitable habitat where they can metamorphose and settle into their juvenile form. This behavior has been seen in fish as well as in the larvae of scleractinian corals. Many families of coral reef fish are particularly attracted to high-frequency sounds produced by invertebrates, which larvae use as an indicator of food availability and complex habitat where they may be protected from predators. It is thought that larvae avoid low frequency sounds because they may be associated with transient fish or predators and is therefore not a reliable indicator of safe habitat.

The spatial range at which larvae detect and use sound waves is still uncertain, though some evidence suggests that it may only be reliable at very small scales. There is concern that changes in community structure in nursery habitats, such as seagrass beds, kelp forests, and mangroves, could lead to a collapse in larval recruitment due to a decrease in sound-producing invertebrates. Other researchers argue that larvae may still successfully find a place to settle even if one cue is unreliable.

Olfaction
Many marine organisms use olfaction (chemical cues in the form of scent) to locate a safe area to metamorphose at the end of their larval stage. This has been shown in both vertebrates and invertebrates. Research has shown that larvae are able to distinguish between water from the open ocean and water from more suitable nursery habitats such as lagoons and seagrass beds. Chemical cues can be extremely useful for larvae, but may not have a constant presence, as water input can depend on currents and tidal flow.

Human Impacts on Sensory Systems
Recent research in the field of larval sensory biology has begun focusing more on how human impacts and environmental disturbance affect settlement rates and larval interpretation of different habitat cues. Ocean acidification due to anthropogenic climate change and sedimentation have become areas of particular interest.

Ocean Acidification
Ocean acidification has been shown to alter the way that pelagic larvae are able to process information and production of the cues themselves. Acidification can alter larval interpretations of sounds, particularly in fish, leading to settlement in suboptimal habitat. Though the mechanism for this process is still not fully understood, some studies indicate that this breakdown may be due to a decrease in size or density of their otoliths. Furthermore, sounds produced by invertebrates that larvae rely on as an indicator of habitat quality can also change due to acidification. For example, snapping shrimp produce different sounds that larvae may not recognize under acidified conditions due to differences in shell calcification.

Hearing is not the only sense that may be altered under future ocean chemistry conditions. Evidence also suggests that larval ability to process olfactory cues was also affected when tested under future pH conditions. Red color cues that coral larvae use to find crustose coralline algae, with which they have a commensal relationship, may also be in danger due to algal bleaching.

Sedimentation
Sediment runoff, from natural storm events or human development, can also impact larval sensory systems and survival. One study focusing on red soil found that increased turbidity due to runoff negatively influenced the ability of fish larvae to interpret visual cues. More unexpectedly, they also found that red soil can also impair olfactory capabilities.