Aquatic pollution is still a serious issue

Tiistai 28.3.2023 klo 15.53 - Mikko Nikinmaa

 In 1970’s and 80’s rivers were little more than sewage channels, and most waste water was pumped out to lakes and seas virtually uncleaned. If strands started to get littered, the solution was to make sewage pipes longer. A standing “joke” was that Americans built holiday resorts to Central America so that whenever the beach started to suffer from municipal pollution, that resort was left to locals and a new one built elsewhere. The polluted rivers could catch fires and fish deaths were common. In the Baltic Sea at least 70 % of the seals could not reproduce, almost causing extinction of Baltic seals.

One would have thought that humankind would have learnt from the problems of the past. But no. Profit is still the major goal; environmental actions are only done, when immediate financial gain would suffer from not doing them. Admittedly, water purification has been much improved in the industrialized countries in fifty years. In part, however, this has meant that the most polluting industry has been relocated to countries with lax environmental regulation. Some rivers in India have so high antibiotic levels that a patient could get a daily dose of medicine by drinking river water, others in Pakistan have so high effluent load from tanning industry that the water colour shows which dye is used most in the textiles. Even in our Western World, many improvements are not real. When it became clear that chlorinated compounds were highly toxic, they were banned. The chemical industry then started producing new fluorinated compounds. Anyone with reasonable knowledge of chemistry could have predicted that since fluorine and chlorine are sister elements, also fluorinated compounds are very toxic. This conclusion was finally reached, and several fluorinated compounds are banned. The insecticide use all over the world has increased, and one of the problems in their use is, if a sweeping generalization is made, that they are much more toxic to aquatic animals than to insects. Also, an occasional spill of toxic substances to rivers still occurs. Add climate change on top of all that, and the present-day situation emerges. The reason for including climate change is that first, the increase in temperature is a stress, and combined with contaminant-induced stresses can cause mortality, and second, climate change causes marked variations of river flow (because of alternations between heavy rains and dry periods) whereby the contaminant flow, e.g., from agriculture becomes highly pulsatile.

One sees the results in the news items. There have been massive fish mortalities in many shallow European lakes and in sea areas at Australian coast. Gold mining effluents have caused fish mortalities in Amazonas area and in Danube. The river Oder (in Poland) experienced major mass mortality of fish last summer and Murray and Darling rivers (in Australia) just recently. While the ultimate reason of neither is clear, agricultural toxicants together with climate change have likely contributed. About 30000 l of styrene leaked last Friday to a tributary of Delaware river, where Philadelphia obtains its drinking water, making it unsuitable for human use for a few days…These are just a couple of examples, it appears that there is an issue with aquatic pollution more or less every day somewhere in the world.

Heart function and individual variability play major roles in temperature tolerance of fish

Maanantai 14.11.2022 klo 14.42 - Mikko Nikinmaa

Climate change has major effects on fish, especially fish in lakes, since the whole water body can warm up as a result of long-lasting heat waves. Because of the uniform temperature regardless of the depth, fish cannot seek colder temperatures near the bottom. As a consequence, massive fish mortalities occur in shallow lakes of temperate zone every summer nowadays.

The reasons, why fish die as a result of increased temperature can only be understood by studying the functional changes occurring as a result of temperature elevation. Thus, physiological studies should be in the centre of climate change studies. If the reasons for vulnerability to increased temperature are known, it can also be estimated, which measurable responses predict fish mortalities. This as a background, and recognizing that individual variability of fish determines why some die and others remain living, we studied how fish tolerant and intolerant to high temperatures differed from each other. The results of the extensive studies are reported by Anttila et al in Comparative Biochemistry and Physiology (//doi.org/10.1016/j.cbpa.2022.111340).

Our results show that for a given age group, heart function is decisive in determining temperature tolerance. The efficiency of heart is markedly different in different individuals, whereby marked individual variability in temperature tolerance occurs. Thus, in predicting the effects of climate change on fish populations, we should not restrict our analysis to the mean response but also to the variability observed. In future it must be evaluated to which extent the thermal tolerance and its variability are heritable, as this will have significant impact on the vulnerability of species to global warming.

Faunal Mortality in Caribbean

Tiistai 19.11.2019 klo 18.33 - Mikko Nikinmaa

In last June-July the news were filled with pictures about Caribbean beaches covered with dead and dying algae. In addition to the beaches, the algae covered the water near them. The large amount of beaching algae has become a yearly problem in 2010’s. Although the aesthetic problems in the beaches (sight and smell) are a major nuisance for areas living on tourism, what happens in coastal waters may be even more alarming for ecosystem health. The decaying algae cause high ammonium and sulphide concentrations in water, and a marked reduction in its oxygen concentration. All these changes are harmful enough to be lethal to large numbers of macrofauna. Especially fish are found dead in large numbers. While the results from last July-August are not yet available, Rodriguez-Martinez et al. have reported the situation in 2018 in Marine Pollution Bulletin 146 (2019) 201–205.

It is probable that this problem is yet another consequence of ongoing climate change. This is an example of effects influencing economies drastically, and the problems are not caused by countries suffering from economic problems. For this reason one needs environmental globalism, the nationalistic populism only worsens the situation. Soon the populist will not have a tourist resort to go to, even if he had saved enough money for it by not accepting the need to do any environmental actions.