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.
Avainsanat: fish mortality, climate change, multiple stresses, insecticides