When you explore a region, roll on the table below to reveal the local ecosystem.
d12 Roll
Ecosystem
1-2
Open water
3
Benthic
4
Mangrove forest
5
Kelp forest
6
Coral reef
7
Underwater settlement
8-9
Vehicle wrecks
10-12
Ruined buildings
Ruined Buildings TBD
Benthic ecosystems are located on the seafloor. The creatures that live here are often very different from the ones found in the open ocean. The exact types of creatures found on the seafloor depends on the depth of the water.
Coral reefs are ecosystems made from exoskeletons secreted by tiny polyps known as coral. The exoskeletons form complex structures that shelter many different organisms. Coral reefs host sponges, crustaceans, mollusks, fish, turtles, sharks, dolphins, and many more creatures. Most coral reefs have been “bleached” and are dead, but you’ve managed to find a living one.
Kelp forests are home to photosynthetic macro-algae, commonly known as “seaweed” or “kelp”. They are often, but not always, anchored to a shallow seafloor. Kelp forests and phytoplankton (micro-algae) are the basis of the marine food web.
Open ocean means the ocean above the seafloor. This is where you can find many creatures we associate with the sea like jellyfish medusae, sharks, and dolphins, but the exact types depend on the depth. Roll on the Depth table to determine how deep the ocean goes.
Vehicle wrecks could be the sunken cars on a submerged freeway, a ship, or even an airplane. Over time, they become encrusted with barnacles and form artificial reefs. Wrecks of all kinds are highly prized for salvage.
Depth
9
Hydrothermal vent
10
Cold seep
Cold seeps
Cold seeps, also known as “cold vents” are areas of the ocean floor where oil, methane, or hydrogen sulfide seepage occurs forming “rivers” or “pools” of brine on the sea floor. Reactions between methane and seawater can also create carbonate rock formations and reefs. Seeps have 10 times the salt concentration of normal seawater, little oxygen, and are toxic to fish.
With the global ban on oil drilling, cold seeps are one of the few ways to legally obtain crude oil and natural gas. In violation of international law, petrochemical companies sometimes set up secret drilling operations in cold seeps, and they don’t take kindly to trespassers.
Hydrothermal vents
Hydrothermal vents are fissures on the seabed that discharge superheated water. This requires a pressure of at least 221.1 bar (3,210 psi) and temperatures of at least 374 C (705 F). Hydrothermal vents are only found near underwater volcanoes and areas of tectonic activity. Minerals dissolved into the water can form stalagmites and other structures that act as homes to tubeworms, crabs, and other animals. They are also great places to build geothermal power plants, but it requires an environmental assessment to do so legally.
2d8 Roll
Depth
1
Photic (< 200 m)
2
Dysphotic (200–1,000 m)
3
Bathyal (1,000–4,000 m)
4
Abyssal (4,000–6,000 m)
5
Hadal (6,000–12,000 m)
16
Supercritical (12,000+ m)
2d8 roll
Depth
Ecosystem
Photic (<200 m)
Mangrove forest
Photic (<200 m)
Kelp forest
Photic (<200 m)
Coral reef
Photic (<200 m)
Ruined buildings
Photic (<200 m)
Vehicle wrecks
Dysphotic (200–1,000 m)
Open water
Benthic
Cold seep
Bathyal (1,000–4,000 m)
Open water
Benthic
Abyssal (4,000–6,000 m)
Hadal (6,000–12,000 m)
d12 Roll
Ecosystem
1-2
Open water
3
Benthic
4
5
6
7
Underwater settlement
8-9
Vehicle wrecks
10-12
Ruined buildings
Photic: Also known as the “epipelagic” or “sunlight” zone, this is where sunlight can easily support photosynthesis.
Dysphotic: Also known as the “mesopelagic” or “twilight” zone. Some light can reach here, but photosynthesis is difficult.
Bathyal: Also known as the “bathylpelagic” or midnight” zone, the Bathyal zone is the first aphotic, or sunless depth.
Abyssal: Also known as the “abbysopelaic” zone.
Hadal: Also known as the “hadopelagic” zone, only found in deep ocean trenches.
Supercritical: Beyond the hadal zone, the ocean temperature increases as it is warmed by the planet’s core.