This is how acidification affects olfaction in marine organisms

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This is how acidification affects olfaction in marine organisms

Acidification can directly affect olfaction in marine organisms. This was reported by the same study published in the The Journal of experimental biology, which tells us how in the past decade, many studies have investigated the effects of low pH / high CO2 as a proxy for ocean acidification on olfactory-mediated behaviors of marine organisms.

The effects of ocean acidification on the behavior of fish vary from very large to none at all, and most of the maladaptive behaviors observed have been attributed to changes in acid-base regulation, leading to changes in ion distribution over neural membranes, and consequently affecting the functioning of gamma-aminobutyric acid-mediated (GABAergic) neurotransmission.

Here, we highlight a possible additional mechanism by which ocean acidification might directly affect olfaction in marine fish and invertebrates. We propose that a decrease in pH can directly affect the protonation, and thereby, 3D conformation and charge distribution of odorants and / or their receptors in the olfactory organs of aquatic animals.

This can sometimes enhance signalling, but most of the time the affinity of odorants for their receptors is reduced in high CO2 / low pH; therefore, the activity of olfactory receptor neurons decreases as measured using electrophysiology.

The reduced signal reception would translate into reduced activation of the olfactory bulb neurons, which are responsible for processing olfactory information in the brain. Over longer exposures of days to weeks, changes in gene expression in the olfactory receptors and olfactory bulb neurons cause these neurons to become less active, exacerbating the problem.

A change in olfactory system functioning leads to inappropriate behavioral responses to odorants. We discuss gaps in the literature and suggest some changes to experimental design in order to improve our understanding of the underlying mechanisms and their effects on the associated behaviors to resolve some current controversy in the field regarding the extent of the effects of ocean acidification on marine fish.

Brine shrimp of Great Salt Lake drowned in mercury and selenium?

The Great Salt Lake is what remains of Lake Bonneville today, a vast prehistoric basin that has largely dried up. The lake is located at an average altitude of 1,280 m.

It has a length of about 120 km and a width that varies between 48 km and 80 km. The average surface area of ​​the lake is 4,400 km², which makes it the second largest lake among those entirely within the borders of the United States, after Lake Michigan, and is subject to strong seasonal variations.

The lake is on average shallow, about 4.5 m. The waters of the Great Salt Lake have a chemical composition very similar to that of ocean waters. The saline concentration varies between 50 g / l and 270 g / l. Due to the high salinity, few living species are able to inhabit it.

The most representative species is constituted by the small crustaceans of the Artemia salina (brin shrimp) species. In summer, the lake attracts tourists and local people, who go there to swim, similar to what happens in the Dead Sea.

The study: Temporal correspondence of selenium and mercury, among brine shrimp and water in Great Salt Lake, Utah, USA, seeks to evaluate the risks that can jeopardize the survival of brine shrimp, in an environment that could be polluted by agents such as precisely selenium and mercury.

Published on the The Science of the total environment, we can read: "The specific source of high burdens of selenium (Se) and mercury (Hg) in several bird species at Great Salt Lake (GSL) remain unknown. Frequent co-located water and brine shrimp samples were collected during 2016 through 2017 to identify potential correlations of element concentrations among brines and brine shrimp, a keystone species in the GSL.

Like many aquatic systems, GSL is characterized by elevated methylmercury (MeHg) in deep waters. in contrast to thermally-stratified aquatic systems, biota in the salinity-stratified GSL do not reside in its deep waters, obscuring the presumed relationship between elevated MeHg in biota and in the deep brine.

Brine shrimp and water column (shallow and deep, filtered and unfiltered) samples were collected from six sites spanning the South Arm of GSL approximately every other month. Mercury concentrations in brine shrimp (on average 89% of which is MeHg) were correlat ed only with total mercury in surface filtered water, and displayed little spatial variability, but consistent seasonal trends across the two sampled years.

In contrast to Hg, temporal correspondence was observed between Se concentrations in brine shrimp and those in all water samples regardless of filtering and depth, with maxima and minima at higher-than-seasonal frequency.

The data suggest a spatially diffuse source of bioavailable mercury to the shallow brine that responds to seasonal influences, for which the underlying deep brine, surficial sediments, and overlying atmosphere were evaluated in terms of potential temporal correspondence to shallow brine and brine shrimp Hg concentrations, as well as potential to mix across the extent of the shallow brine.

Bioaccumulation factors were at the low end of those reported for marine systems, and decreased at higher trace element concentrations in water. "