Algal transect surveys (MEP)


I repeatedly survey permanent cross-stream transects (“x-scns”) to follow changes in algae, environmental conditions, and associated organisms over time, documenting seasonal and interannual variation. Transects are benchmarked at both ends with nails in trees or bedrock—these can be labeled with aluminum tree tags (Forestry Supply) and should be carefully located with hand-drawn maps, GPS, triangulation (measure distance to spot from two other conspicuous landmarks), etc.   Benchmarks should be on ‘permanent’ structures (e.g. large trunks) high enough so that high as well as low flows can be documented (just above bank full is ideal, higher than that and it’s hard to read the tape while walking the streambed). On each survey, stretch a meter tape tightly between the nails. Nail to nail distance should vary less than 1 cm over repeated surveys. Take enough points to obtain about 15-20 measurements for each x-scn. At 0.5 m or 1.0 m intervals along each transect:

  1. note distance along the meter tape (X-strm (m))
  2. measure water depth (cm) (a ski pole marked in decimeters is good, doesn’t flex in high flow, and saves you from falls)
  3. measure velocity with a current meter, or estimate surface current velocity (cm s-1) by timing floating objects across your measurement point1
  4. note dominant and subdominant substrate particle sizes2
  5. using a diving mask or plexiglass view box, note the dominant and subdominant macroscopic algal taxa within an estimated 10 cm x 10 cm area around each sampling point3
  6. record the modal height (cm) of attached filaments or the length from point of attachment of strands of algae floating over the site on the water surface, if these obscured view of the bed.
  7. characterize algal density (% cover) 4
  8. if possible (for Cladophora, zygnematales, perhaps Nostoc) characterize algal condition5
  9. note conspicuous animals within the same 100 cm2 observation area, bearing in mind that some will be attracted to you (minnows) and others will be hiding (mayflies) 6.



Key–Codes and categories used:


  1. Flow velocity (cm s-1) (surface velocity)


0          0 (silt settles vertically)

5          0-5

10        5-10

20        10-20

30        20-30

50        30-50

100      50-100



  1. Particle size (median diameter, mm)


M      <<< 2 mm, not gritty = mud

S       < 2, gritty = sand

G        2-16 =     gravel

P        16-64 =   pebbles

C         64-256 =   cobbles

B        > 256 but separate = boulder

Br        continuous with landscape = bedrock



  1. Algal (etc.) codes


Clad                 Cladophora (note color as green G, yellow Y or Rusty red R)

Moug, Spg     Mougeotia or Spirogyra (need to distinguish under scope)

Zyg                Zygnema (more chatreuse than Spg or Moug, colder water)

diat sk            diatom skin (gold, orange or yellow-brown)

bg sk                dark or grey skin (often Phormidium, Tolypothrix or Scytonema)

Nos b              Nostoc balls (if just “Nos” is written, assume balls)

Nos e               Nostoc ears (colonized and resculpted by Cricotopus midge larvae)

Riv                  Rivularia black freckles to larger circular spots or blotches

Anab               deep turquoise to black Anabaena, loosely epiphytic on Clado

Phor                Phormidium—dark brown epilithic cyanobacteria turf in riffle flow

Silt                   deposited organic detrital floc

Sedge              dominant bunched graminoid along active channel is Carex nudata

Moss               Fontinalis is long flowing moss up to 60 cm, other riverine mosses are mats

Leaves             Terrestrial leaf litter

Alder green       we have noted some years if the dominant alders drop green leaves

Alder brown    these alder leaves would add less nitrogen to the river



  1. Algal density


1         a few filaments

2        < 10% basal cover

3        10-50% basal cover

4         50-98% cover

5          can’t see substrate through growth



  1. Algal condition


1         nearly detritus

2         senescent, discolored, fragile and falling apart

3         discolored but less fragile

4         slightly discolored, but robust

5          vibrantly healthy



  1. commonly observed Fauna (optional)


tufts (retreats of Pseudochironomus)

tube midges

Pet Petrophila, aquatic moth larvae, clear as larva, white scabs as pupa



Hept – heptageniids

Baet – baetids (Baetis, Centroptilum)

Ephem –ephemerellids

Siph – siphlonurids

Leps –Leptophlebiiids



Dicos     Dicosmoecus caddisflies see illustrations of 5 larval instars

Oncos   Oncosmoecus, similar with no saddlebag pebs at rounder aperture

Tin         Tinodes tube dwelling caddis, like spaghetti

Leuco      rice grain size sessile caddis

Gum         Gumaga, slender curved sand cases

Neo          Neophylax, stone cylindrical case

Glosso       Glossosoma, turtle shell stone case



Rams –      Helisoma



Ferrissia — fw limpets



R roach

Stl steelhead

Stk stickleback

PM pike minnow

Su  sacramento suckers