So do the egg and juvenile life stages of other fish species. Aquatic organisms that need the most oxygen will suffocate first, reducing the food choices for surviving species. If the oxygen drain continues, more species will perish, reducing the food choices further. In Massachusetts, late summer is a stressful time for fish, as water levels drop, water temperatures rise, and dissolved oxygen levels decrease. Added organic or nutrient loads can cause fish kills.
Sewage also brings in bacteria and pathogens, making the water unsafe to drink or swim.
Natural droughts in late summer can be exacerbated by withdrawals of water from the river directly or through groundwater wells. Shallower waters and lower flows mean less living space is available to fish and other aquatic organisms, increasing competition for food and predation. Lower oxygen levels and increased temperatures stress fish, making them more susceptible to bacterial infections. Not only do these individual actions cause impacts, there is a cumulative impact that may go far beyond the sum total of the individual impacts. Most any river in Massachusetts has been subjected to this treatment at some time it its relationship with humans.