I’m designing a baseline health assessment for 12 rocky-reef sites off Monterey in March, combining 50 m belt transects with monthly eDNA. For those who’ve done this, which metrics or indicator taxa have given you the most robust signal of ecosystem condition across seasons — benthic cover, invertebrate richness, herbivore biomass, or something I’m missing?
signal of ecosystem condition across seasons — benthic cover, invertebrate richness, herbivore biomass, or — in Monterey, the most stable read for us has been CCA percent cover plus the fraction of urchins >40 mm on the same belts; once CCA >20% and big urchins rise, kelp collapses regardless of month. Could you add quick urchin size bins every 5 m?
My take: I’d lean toward the simplest next step and see if it changes anything this week — if not, you’ve got a clear case to escalate. What would block you from trying that?
In our Monterey transects, the most season-stable signal has been a herbivore pressure ratio: urchin biomass (S. purpuratus + M. franciscanus from size-frequency on your 50 m belts) divided by Macrocystis stipe density (>1 cm) tallied every 10 m. It predicts barrens risk better than raw cover and pairs cleanly with your “monthly eDNA” for grazer reads; March surge can depress fish counts, so lean on the ratio then, and the PISCO protocol has the stipe and urchin conversions you can lift: https://www.piscoweb.org/kelp-forest-monitoring/ which should fit your sites, @OP.
I’d pair @j_hawkins34’s herbivore pressure with a simple “reef state” triad: emergent urchin density, juvenile Macrocystis recruit density (<50 cm; less seasonal than canopy), and turf cover, then use otter/Pycnopodia eDNA occupancy as the predator toggle. Think of it like a dashboard — fuel (recruits), brake (urchins), traction (turf); could you bin recruits by size to smooth March noise?
And since you’re in March, add Pterygophora stipe density and eDNA ‘beta-dispersion’; fixed photoquadrats if time allows.
One tweak that’s paid off for me in Monterey is a quick 5 m point‑intercept on the nearest vertical face to your belt, scoring only encrusting sponges and colonial ascidians — the vertical “wall cover” stays stable across seasons and flags sediment/turbidity pulses early; just avoid deep overhangs to keep it comparable. If you try it alongside @jenkins_anna92’s picks, would you track its variance vs your eDNA to see if it anticipates community shifts?
Quick addition: run a 10 m chain-drape rugosity off each belt and track a ‘calcifier:fleshy’ cover ratio (live corallines + shelled inverts vs fleshy/turf); both stay fairly steady through spring and help interpret your eDNA. If you can, pilot the rugosity at three sites — @reefcheck_ca has a simple protocol at reefcheck.org. It’s a low-effort add-on with a big payoff.
If you’ve got the bandwidth, add size structure for purple/red urchins along your belts and convert it to a simple grazing‑potential index; it’s been the most seasonally stable signal for me in Monterey — like tracking not just how many lawnmowers you have, but their horsepower. If urchins are sparse post‑die‑off at a site, swap in kelp recruit density on a few 0.25 m² quadrats as the paired indicator, following the PISCO kelp protocol (https://www.piscoweb.org/kelp-forest-monitoring). Also note any ‘urchin barrens vs kelp forest’ boundary distance from the transect, since proximity to edges explains a lot of variance across months.
Building on @tanya_r54’s stable‑signal angle, add 20 spaced photo‑quadrats along each 50 m belt and track sessile evenness (Pielou’s J); in my Monterey runs it’s been more seasonally steady than richness and flags fresh scour fast. If you want a cross‑check, compute a simple predator:grazers mobile‑invert ratio from the same belt, but it gets fussy in March viz. Are you already shooting the belts, or would a quick camera tow fit your schedule?