How Could People Utilize a Hypereutrophic Sea?

Question

In a previous post I asked about the feasibility of connecting the ocean to a dried sea bed with hand tools and it was pointed out how environmentally disastrous this would be.

So the bronze age geo-engineers got their wish and flooded a desert with salt water. Now they have a huge salt lake with minimals outflow and significant inflow from the ocean and a few rivers that fed some preexisting salt lakes in the basin.

The sand and desert rock had quite a bit of phosphorus in them, which coupled with the lack of outflow has made the waters perfect for algal blooms. The blooms are so great and frequent that there are very few fish at all, and the ones that are present are dangerous for human consumption. There are such great concentrations of algae year round that the sea has a sickly green color.

So how can humans who have been pushed from their oasis homes adapt to life alongside a massive salt water lake that has practically no fish? What resources could they glean from such a vile place?

Note: They have access to fresh water from the inflowing rivers but they can’t settle far from the coast due to hostile neighbors.

Answer 1

Puppetsock's answer is great. I have a few things to add.

Your Bronze age people are going to need some things to make use of the inland sea they have created. The first thing, as is all survival scenarios, is drinkable water. They are going to have to create some stills to get drinkable water. If you want them to get kind of steampunky you could do this fairly easily.

First, they make a concave reflector or reflectors to act as a means to focus sunlight on a point. Then make a traditional still, with a boiler and some condensation coils and a vessel to catch the purified water. The reflectors focus the sunlight on the boiler that is filled with the nasty water from the inland, salty, nasty algae sea. The focused light brings the water to a boil, destroying the impurities and leaving you with nice, drinkable water. I'm talking about using solar power primarily because fuel for a fire might be pretty precious. Obviously the boiler would need to be cleaned pretty often, but you have a method to get drinking water.

The sludge from the boilers might be useful as a fertilizer for crops. Not 100% sure on that because I'm not a big agricultural guy. It may need to be combined with night soil for compost.

Your people might even be able to use aquaculture to create Duckweedfarms for food. Duckweed may be a way to help remove the phosphorous from the water if you can create pools away from the sea to use for this. the water could then have an outflow into whatever small croplands you have available.

The population will be neccesarily small, but could potentially thrive.

Answer 2

What you describe is very similar to the Dead Sea.

The Dead Sea is called "dead" because there are no macroscopic organisms. No fish, no plants, no algae. There is a small amount of microscopic life. When rainwater lowers the salt content there can be a "bloom" of bacteria that temporarily flourish. But the low range of salt content is round about 30%. So it is an unusual bacteria that can survive at all.

The primary useful aspects of the dead sea include extraction of minerals and tourism.

There is also a project to generate electricity. The idea is, water from the Mediterranean Sea would flow into the Dead Sea, moving downwards about 430 meters. This is about seven times as high as Niagara Falls. So sea water would be allowed to enter, and then encouraged to evaporate in the Dead Sea using evaporation ponds. This would replenish the sea, which has been lowering substantially in level in the last few decades. And it would generate hydro power.