Berau Post merilis bahwa kejadian di Berau dengan perubahan warna sungai dan kematian biotanya diakibatkan oleh cyanobacteria. Sumber dari internet dan kutipan riset berbagai Universitas di dunia menyebutkan bahwa bakteri ini sudah ada sejak 3, juta tahun yang lalu. Bakteri inilah yang menjadi awal dalam teori evolusi karena dapat hidup di wilayah beroksigen rendah dan kemudian melakukan fotosintesa untuk menghasilkan oksigen. Siklus hidup bakteri ini yang pendek kemudian menjadi masalah karena ketika mati proses peruraiannya menggunakan oksigen.

Perubahan warna air sungai Segah menjadi hijau dan diikuti kematian semua jenis ikan, termasuk ikan gabus dan lele, disebabkan keberadaan cyanobacteria. Cyanobacteria atau sianobakteria adalah sebuah filum bakteri yang mendapatkan kebutuhan energinya melalui fotosintesis. http://www.beraupost.co.id/berita/detail/disebut-faktor-cyanobacteria.html

Yang berbahaya adalah ketika populasi ini berkembang sangat cepat atau proses nya disebut blooming. Kandungan phospor dan amoniak yang tinggilah yang menyebabkan perkembangan cyanobacteria. 

Cyanobacteria can produce neurotoxins, cytotoxins, endotoxins, and hepatotoxins (i.e. the microcystin-producing bacteria species microcystis), and are called cyanotoxins.

Specific toxins include, anatoxin-a, anatoxin-as, aplysiatoxin, cyanopeptolin, cylindrospermopsin, domoic acid, nodularin R (from Nodularia), neosaxitoxin, and saxitoxin. Cyanobacteria reproduce explosively under certain conditions. This results in algal blooms, which can become harmful to other species, and pose a danger to humans and animals, if the cyanobacteria involved produce toxins. Several cases of human poisoning have been documented, but a lack of knowledge prevents an accurate assessment of the risks.[48][49][50] Recent studies suggest that significant exposure to high levels of some species of cyanobacteria producing toxins such as BMAA can cause amyotrophic lateral sclerosis (ALS). The Lake Mascoma ALS cluster [51] and Gulf War veterans’ cluster are two notable examples.[49][50][52]”sumber: https://en.wikipedia.org/wiki/Cyanobacteria

Freshwater algal blooms are the result of an excess of nutrients, particularly some phosphates.[2][3] The excess of nutrients may originate from fertilizers that are applied to land for agricultural or recreational purposes. They may also originate from household cleaning products containing phosphorus.[4] These nutrients can then enter watersheds through water runoff.[5] Excess carbon and nitrogen have also been suspected as causes. Presence of residual sodium carbonate acts as catalyst for the algae to bloom by providing dissolved carbon dioxide for enhanced photo synthesis in the presence of nutrients. sumber: https://en.wikipedia.org/wiki/Algal_bloom

Phospate sekali lagi harus dilihat lebih detail karena ini bisa saja dihasilkan dari proses pertambangan misalnya pertambangan

Phosphate deposits can contain significant amounts of naturally occurring heavy metals. Mining operations processing phosphate rock can leave tailings piles containing elevated levels of cadmium, lead, nickel, copper, chromium, and uranium. Unless carefully managed, these waste products can leach heavy metals into groundwater or nearby estuaries. Uptake of these substances by plants and marine life can lead to concentration of toxic heavy metals in food products. In Germany, the use of uranium-contaminated standard phosphate fertilizers in farming has been linked to significantly raised uranium levels in drinking water.[15] In some areas, it has led to recommendations to use bottled water, instead of tap water, to prepare food for babies and small children. sumber: https://en.wikipedia.org/wiki/Phosphate

Sekali lagi menurut saya yang perlu di uji secara detail  adalah kandungan logam, kandungan material di air, bukan hanya ikan atau biota yang mati saja. Dan ini dilakukan pada lokasi lokasi yang merupakan penyebab kandungan phospate dan amoniak.