Ocean warming undermines the recovery resilience of New England kelp forests following a fishery-induced trophic cascade

Ecological theory predicts that kelp forests structured by trophic cascades should experience a recovery and persistence of their foundation species when herbivores become rare. Yet, climate change may be altering the outcomes of top-down forcing in kelp forests, especially those located in regions that have rapidly warmed in recent decades, such as the Gulf of Maine. Here, using data collected annually from 30+ sites spanning >350 km of coastline, we explored the dynamics of Maine’s kelp forests in the ~20 years after a fishery-induced elimination of sea urchin herbivores. Although forests (dominated by Saccharina latissima and Laminaria digitata) had broadly returned to Maine in the late 20th century, we found that forests in northeast Maine have since experienced slow but significant declines in kelp, and forest persistence in the northeast was juxtaposed by a rapid, widespread collapse in the southwest. Forests collapsed in the southwest apparently because ocean warming has – dir..., Methods for: Quantifying kelp forest trajectories through time and space
Associated files:
DMR_benthicsurvey_algae_urchin_randomsites_alldepths_2001_2018.csv ;
Rasher_Steneck_benthicsurvey_algae_urchin_allsites_alldepths_2016.csv ;
Rasher_Steneck_benthicsurvey_algae_urchin_allsites_alldepths_2017.csv ;
Rasher_Steneck_benthicsurvey_algae_urchin_allsites_alldepths_2018.csv
To quantify changes in Maine’s kelp forests through time and space, we conducted in situ surveys (via SCUBA) of rocky reefs every year from 2001 to 2018 (via long-term monitoring by the Maine Department of Marine Resources; hereafter “ME-DMR”).  From May to June of each year, ME-DMR divers visually surveyed up to 140 randomly selected sites, some of which were sheltered from waves and/or in rivers or estuarine environments and were subsequently excluded from our analysis (see below and associated code).  At each site, the diver began their survey at 15 m depth (mean lower low water, hereafter “MLLW”) and swam perpend..., , # Ocean warming undermines the recovery resilience of New England kelp forests following a fishery-induced trophic cascade

[https://doi.org/10.5061/dryad.v9s4mw73q](https://doi.org/10.5061/dryad.v9s4mw73q)

## Description of the datasets and file structures

Below, find the metadata for columns in each raw data file:

### DMR\_benthicsurvey\_algae\_urchin\_randomsites\_alldepths\_2001\_2018.csv

* year - Integer for year.
* date - Date in M/D/Y format.
* site.number - Integer identifier for site. Numbers were reused between years, but do not correspond to the same sites.
* region.code - Integer code of DMR management area. Does not match region. Not used in analyses.
* region - Character identifier for name of region on the coast of Maine.
* exposure.code - Integer identifier for 1-5 qualitative scale of total arc (in degrees) where a site was exposed to the open ocean.
* coastal.code - Integer identifier for 1-5 qualitative scale of a site's coastal status. Exposed mainl...