Ecosystem · 7.216 measured places · 9 kinds of water

The Netherlands has no single underwater world

Pick a kind of water and see where in the country it lies — and what four different survey methods found living in it.

Four ways of looking

These are not groups of creatures — they are field methods. Each returns organisms the others never see, which is why a water is described four times over rather than once.

1
Micro-life

a bottle of water under the microscope

3.598 places
2
Bottom life

a kick-net across the bed

4.641 places
3
Plants

a rake through the water plants

7.216 places
4
Fish

a fyke net or an electro-fishing run

2.745 places

Where a way of looking was never used at a water, we say so rather than guess. “Nobody looked” and “nothing lives there” are different statements, and only one of them is ours to make.

The 9 waters of the Netherlands

Each of these is a kind of water, not a kind of creature: how it formed, what colour it runs, how wide and how salt. Every measured place is sorted into one from the landscape it lies in and the water body it lies on — and then the four field methods report what they found there.

Brown as tea, and not dirty

The peat water

Where peat was cut for centuries, pools were left behind with a bed of peat rather than sand. The water stains dark brown because it dissolves humic acids out of that peat — not pollution, but the colour of the ground itself. Little light gets through, so plants stay near the surface and the bottom is soft, black and deep.

This is sheltered water: narrow strips, wide reed margins, almost no wave action. Frogbit and flowering rush belong here, and most of what lives in it sits among their roots.

Micro-life 39 families per place across 146 places
Bottom life 52 families per place across 98 places
Plants 37 species per place across 399 places
Fish 10 species per place across 106 places

Diatoms Bacillariaceae
Blue-green algae Pseudanabaenaceae
Green algae Dunaliellaceae
Golden algae Mallomonadaceae
Euglenoids Phacidae
Non-biting midges Chironomidae
Mesh-web spiders Dictynidae
Creeping water bugs Naucoridae
Water beetles Noteridae
Opossum shrimps Mysidae
Reed sweet-grass Glyceria maxima
Nodding bur-marigold Bidens cernua
Tubular water-dropwort Oenanthe fistulosa
Flowering rush Butomus umbellatus
Frogbit Hydrocharis morsus-ranae
Perch Perca fluviatilis
Pike Esox lucius
Roach Rutilus rutilus
Rudd Scardinius erythrophthalmus
Crucian Carp Carassius carassius
Tubenose goby Proterorhinus marmoratus
European bitterling Rhodeus amarus
Spined loach Cobitis taenia
Ruffe Gymnocephalus cernuus

Flowing, clear and cooler than the rest

The sand stream

On the higher sandy soils, streams run over clean sand and gravel. The water is clear because the current carries the fine silt away rather than letting it settle, and in summer it stays a few degrees cooler than standing water.

Current demands a different kind of animal: everything here must hold on or hide. Caddisflies build cases of sand grains against a stone, brook water mites crawl between them, and blackflies filter the current with fans. That is a company you never meet in a ditch.

Micro-life 24 families per place across 186 places
Bottom life 56 families per place across 389 places
Plants 35 species per place across 562 places
Fish 12 species per place across 502 places

Diatoms Bacillariaceae
Acid-water diatoms Eunotiaceae
Chain-forming diatoms Melosiraceae
Attached diatoms Cocconeidaceae
Golden algae Mallomonadaceae
Non-biting midges Chironomidae
Net-spinning caddisflies Hydropsychidae
Stream water mites Sperchontidae
Blackflies Simuliidae
Water mites Hygrobatidae
Reed canary grass Phalaris arundinacea
Unbranched bur-reed Sparganium emersum
Water-starwort Callitriche
Arrowhead Sagittaria sagittifolia
Water forget-me-not Myosotis scorpioides
Roach Rutilus rutilus
Pike Esox lucius
Perch Perca fluviatilis
Gudgeon Gobio gobio
Stream bullhead Cottus rhenanus
Eurasian Minnow Phoxinus phoxinus
Atlantic Salmon Salmo salar
Barbel Barbus barbus
Wels Catfish Silurus glanis

Acidic, nutrient-poor, and remarkable for it

The moorland pool

A moorland pool sits on heathland over a layer that holds water back, so it is fed by rain alone. Rain carries almost nothing — no lime, barely any nutrients — which leaves the water acidic and exceptionally poor.

That poverty is exactly what produces species that can live nowhere else. Sphagnum forms the floating margin, and the water holds dragonfly and damselfly larvae — chasers and emerald damselflies — and caddisflies that tolerate the acidity. These are small waters with short species lists, and almost every name on the list is one you will not find elsewhere.

Micro-life 23 families per place across 40 places
Bottom life 44 families per place across 161 places
Plants 28 species per place across 137 places
Fish 8 species per place across 84 places

Diatoms Bacillariaceae
Acid-water diatoms Pinnulariaceae
Chain-forming diatoms Melosiraceae
Attached diatoms Cocconeidaceae
Flagellates Cryptomonadaceae
Non-biting midges Chironomidae
Stream water mites Sperchontidae
Chaser dragonflies Libellulidae
Emerald damselflies Lestidae
Net-spinning caddisflies Hydropsychidae
Soft rush Juncus effusus
Marsh pennywort Hydrocotyle vulgaris
Floating sweet-grass Glyceria fluitans
Yellow loosestrife Lysimachia vulgaris
Water plantain Alisma plantago-aquatica
Pike Esox lucius
Perch Perca fluviatilis
Nine-spined stickleback Pungitius pungitius
Roach Rutilus rutilus
Pumpkinseed Lepomis gibbosus
Eastern mudminnow Umbra pygmaea
Three-spined stickleback Gasterosteus aculeatus
Bleak Alburnus alburnus
Tubenose goby Proterorhinus semilunaris

Shallow, open and never still

The large lake

The big Dutch lakes are strikingly shallow for their size. That lets wind reach the whole water column: little settles, silt stays suspended, and the water is rarely clear. A sheltered shore and a windward one can hold completely different water on the same day.

Shallow, open and nutrient-rich is exactly what algae want. In summer the water turns green, and every pole and stone carries zebra mussels filtering that water back out.

Micro-life 43 families per place across 336 places
Bottom life 41 families per place across 174 places
Plants 26 species per place across 251 places
Fish 10 species per place across 272 places

Diatoms Fragilariaceae
Green algae Characiaceae
Water net alga Hydrodictyaceae
Blue-green algae Pseudanabaenaceae
Planktonic algae Chrysochromulinaceae
Non-biting midges Chironomidae
Opossum shrimps Mysidae
Mud shrimps Corophiidae
Zebra mussels Dreissenidae
New Zealand mud snail Tateidae
Common reed Phragmites australis
Fragile stonewort Chara globularis
Lesser bulrush Typha angustifolia
Horned pondweed Zannichellia palustris
Nodding bur-marigold Bidens cernua
Perch Perca fluviatilis
Roach Rutilus rutilus
Pike Esox lucius
Bream Abramis brama
Caucasian Dwarf Goby Knipowitschia caucasica
Bullhead Cottus gobio
Ruffe Gymnocephalus cernuus
Round goby Neogobius melanostomus
Zander Sander lucioperca

The most common water in the country

The polder ditch

Most Dutch surface water is not lake but ditch: narrow, shallow, over clay or peat, with a water level set by a pumping station rather than by nature. There is almost no current and the banks are steep.

Such a ditch looks unremarkable and is — but it is the water most people in this country walk past and fish. Duckweed closes the surface in summer, and beneath it lives a company that copes well with that: water snails and bladder snails, leeches, bitterling and spined loach.

Micro-life 30 families per place across 207 places
Bottom life 51 families per place across 127 places
Plants 32 species per place across 288 places
Fish 11 species per place across 139 places

Diatoms Bacillariaceae
Attached diatoms Cocconeidaceae
Chain-forming diatoms Melosiraceae
Euglenoids Phacidae
Volvox colonies Volvocaceae
Non-biting midges Chironomidae
Fish leeches Piscicolidae
Mussel mites Unionicolidae
Water snails Valvatidae
Bladder snails Physidae
Common duckweed Lemna minor
Canadian waterweed Elodea canadensis
Rigid hornwort Ceratophyllum demersum
Common stonewort Chara vulgaris
Flowering rush Butomus umbellatus
Perch Perca fluviatilis
Pike Esox lucius
Roach Rutilus rutilus
Rudd Scardinius erythrophthalmus
Grass Carp Ctenopharyngodon idella
Tubenose goby Proterorhinus marmoratus
European bitterling Rhodeus amarus
Spined loach Cobitis taenia
Belica Leucaspius delineatus

Brown, powerful, full of newcomers

The big river

The Rhine and Maas carry sand and silt out of half of Europe. The water is turbid and the bed shifts constantly, except where groynes and quarry stone lie. That hard substrate is rare in a sand-bedded river and is therefore crowded.

It is also the water where things change fastest. Shipping brought in zebra mussels, mud shrimps and gobies, and they now sit on almost every stone. That makes the river the most unmistakable water in the country: this combination occurs nowhere else.

Micro-life 45 families per place across 330 places
Bottom life 48 families per place across 351 places
Plants 32 species per place across 478 places
Fish 12 species per place across 451 places

Diatoms Bacillariaceae
Green algae Dunaliellaceae
Volvox colonies Volvocaceae
Flagellates Pyrenomonadaceae
Golden algae Mallomonadaceae
Non-biting midges Chironomidae
Mud shrimps Corophiidae
Zebra mussels Dreissenidae
Basket clams Cyrenidae
Opossum shrimps Mysidae
Reed sweet-grass Glyceria maxima
Arrowhead Sagittaria sagittifolia
Cyperus sedge Carex pseudocyperus
Water dock Rumex hydrolapathum
Flowering rush Butomus umbellatus
Perch Perca fluviatilis
Roach Rutilus rutilus
Pike Esox lucius
Bream Abramis brama
Bighead goby Neogobius kessleri
Round goby Neogobius melanostomus
Monkey goby Neogobius fluviatilis
Asp Aspius aspius
Wels Catfish Silurus glanis

Neither fresh nor salt, and singular for it

The brackish water

In the delta and along the coast, seawater mixes with river water. Salinity shifts with the tide and with river flow, and that shifting is the hardest thing an aquatic animal can face — you have to cope with both.

So the species list is short but entirely its own: species that manage in neither pure fresh nor pure salt have the place to themselves. Widgeon grass on the sand, shrimps and crabs among it, gobies and smelt in the open water.

Micro-life 43 families per place across 197 places
Bottom life 39 families per place across 167 places
Plants 25 species per place across 107 places
Fish 12 species per place across 161 places

Diatoms Bacillariaceae
Flagellates Pyrenomonadaceae
Volvox colonies Volvocaceae
Green algae Dunaliellaceae
Euglenoids Phacidae
Non-biting midges Chironomidae
Basket clams Cyrenidae
Zebra mussels Dreissenidae
Mud shrimps Corophiidae
New Zealand mud snail Tateidae
Common duckweed Lemna minor
Horned pondweed Zannichellia palustris
Rigid hornwort Ceratophyllum demersum
Common reed Phragmites australis
Water dock Rumex hydrolapathum
Perch Perca fluviatilis
Roach Rutilus rutilus
Bream Abramis brama
Pike Esox lucius
Prussian carp Carassius gibelio
Asp Aspius aspius
Zander Sander lucioperca
Ide Leuciscus idus
Monkey goby Neogobius fluviatilis

Where you can still see the bottom

The clear sand water

Sand extraction left deep lakes with steep sides and a clean sand bed. Little nutrient comes in and little settles, so the water stays clear in a way that is rare in this country — you can see metres down.

Clear water means light reaches the bed, which is exactly what stoneworts need. They form a low carpet on the sand that binds the silt and keeps the water clearer still. It is one of the few places in the Netherlands where you can watch something standing underwater.

Micro-life 32 families per place across 204 places
Bottom life 46 families per place across 244 places
Plants 29 species per place across 246 places
Fish 10 species per place across 154 places

Diatoms Bacillariaceae
Acid-water diatoms Pinnulariaceae
Green algae Characiaceae
Blue-green algae Microcystaceae
Planktonic algae Chrysochromulinaceae
Non-biting midges Chironomidae
Emerald damselflies Lestidae
Chaser dragonflies Libellulidae
Phantom midges Chaoboridae
Aquatic worms Lumbriculidae
Soft rush Juncus effusus
Marsh pennywort Hydrocotyle vulgaris
Yellow loosestrife Lysimachia vulgaris
Common spike-rush Eleocharis palustris
Water-starwort Callitriche
Pike Esox lucius
Perch Perca fluviatilis
Roach Rutilus rutilus
Tench Tinca tinca
Eastern mudminnow Umbra pygmaea
Pumpkinseed Lepomis gibbosus
Chub Leuciscus cephalus
Nine-spined stickleback Pungitius pungitius
Three-spined stickleback Gasterosteus aculeatus

Salt, never still, and different twice a day

The sea

Beyond the dunes and the sea dikes begins water that has nothing in common with anything inland. It is salt, it never stops moving, and on the Wadden Sea and in the Zeeland delta it falls dry twice a day and fills twice a day. What looks like one flat area on a map is really a landscape of channels, sandbanks and mudflats that changes shape every tide.

The life here is built for that. Flatfish bury themselves and let the tide pass over them; shrimp and young fish ride the rising water onto the flats to feed and drop back as it falls. The shallows are a nursery: plaice, sole and herring all start small here before moving into the deeper North Sea.

Micro-life barely surveyed this way only 2 places
Bottom life barely surveyed this way only 1 places
Plants barely surveyed this way only 1 places
Fish 11 species per place across 299 places

European plaice Pleuronectes platessa
Atlantic herring Clupea harengus
Common sole Solea solea
European Flounder Platichthys flesus
Scaldfish Arnoglossus laterna
Reticulated Dragonet Callionymus reticulatus
Fourbeard Rockling Enchelyopus cimbrius
Grey Gurnard Eutrigla gurnardus
Lange schar Hippoglossoides platessoides

How we know this

Where it comes from

National water-quality monitoring: every water board and Rijkswaterstaat, delivered as open data. Not angler reports and not casual observations — surveys with a method behind them, so that two places can be compared at all.

Why four descriptions and not one

A single combined type was tested and rejected: it turned out to say more about which organisation sampled a water than about the water. Keeping the four separate is the honest version — and it reads better anyway, because each one is a sentence you can check against the creatures listed beside it.

Why some waters have no name here

A type is only named when a distinct set of species marks it out. Many waters are simply ordinary, and that is a real answer rather than a gap — an unremarkable ditch is genuinely unremarkable, and inventing a label for it would be the least trustworthy thing on this page.

What the measurements cannot tell you

Different measurements at one water can be years apart, because the programmes behind them ran at different times. The types describe what kind of water it is, not what happened there last season, and nothing here should be read as a trend.

Last recalculated: 2026-09-12