DOI: 10.5061/dryad.5q83s
title: Data from: Invasive bryozoan alters interaction between a native grazer and its algal food

description: The epiphytic bryozoan Membranipora membranacea encrusts the surface of
 kelp blades, causing recurrent large-scale defoliation events in kelp beds
 off the Atlantic coast of Nova Scotia, Canada. The gastropod Lacuna vincta
 grazes kelp, creating perforations that weaken blade tissues and increase
 the fragmentation rate. We assess the interaction between M. membranacea
 and L. vincta by measuring the grazing rate of snails on
 bryozoan-encrusted and non-encrusted kelp (Saccharina latissima) in
 no-choice and choice experiments in the laboratory conducted in November
 and December 2010. There was no effect of diet on grazing rate in
 no-choice experiments. In choice experiments, however, L. vincta grazed
 significantly more non-encrusted than encrusted kelp (7.1 versus 1.1 mg
 snail−1 d−1), and grazing rate of non-encrusted kelp was almost twice that
 in the no-choice experiment (3.8 mg snail−1 d−1), indicating that snails
 may avoid colonies of M. membranacea on partially encrusted kelp blades.
 We found no effect of diet on growth, reproduction and survival of snails
 maintained for four weeks on encrusted or non-encrusted kelp. By
 concentrating grazing damage on non-encrusted areas of blades, L. vincta
 may act synergistically with M. membranacea to increase the likelihood of
 blade breakage and canopy loss. This indirect effect of the invasive
 bryozoan could augment its direct effect on the standing biomass of native
 kelp beds and detrital export to adjacent communities.
description: Single diet feeding
 experiment data from: Invasive bryozoan alters interaction between a
 native grazer and its algal food. A Canadian Healthy Oceans Network
 Ecosystem Function Project, EF-11.Rate of mass change
 (mg/day) of kelp tissue disks (Saccharina latissima) in experimental
 feeding arenas in the laboratory containing snails (Lacuna vincta) offered
 one dietary item and autogenic control arenas with no snails. Data for
 each replicate container includes herbivore absence/presence, diet (kelp
 encrusted by invasive bryozoan M. membranacea or non-encrusted kelp), and
 rate of mass change of kelp disk.single_diet_exp_data.csvMixed diet feeding experiment data from: Invasive bryozoan alters interaction between a native grazer and its algal food. A Canadian Healthy Oceans Network Ecosystem Function Project, EF-11.Rate of mass change (mg/day) of kelp tissue half disks (Saccharina latissima) in feeding arenas in the laboratory with snails (Lacuna vincta) offered dietary choice of kelp encrusted by invasive bryozoan M. membranacea or non-encrusted kelp simultaneously and in autogenic control arenas with no snails. Data include arena identity, herbivore absence/presence, dietary item (encrusted/non-encrusted), rate of mass change of kelp tissue.mixed_diet_exp_data.csvSnail growth data from: Invasive bryozoan alters interaction between a native grazer and its algal food. A Canadian Healthy Oceans Network Ecosystem Function Project, EF-11.Weekly measures of shell height (mm) of individual snails (Lacuna vincta) maintained in feeding arenas in the laboratory over 4 weeks on single diets of either kelp (Saccharina latissima) encrusted by the invasive bryozoan M. membranacea, non-encrusted kelp, or starved. Data include arena identifier, individual identifier (nested within arena), diet, initial shell height (mm), and shell heights at the end of weeks 1-4 (mm).growth_data_lacuna.csvSnail egg mass production data from: Invasive bryozoan alters interaction between a native grazer and its algal food. A Canadian Healthy Oceans Network Ecosystem Function Project, EF-11.Egg mass production between weeks 3 and 4 of snails (Lacuna vincta) maintained in feeding arenas over 4 weeks on single diets of either kelp (Saccharina latissima) encrusted by the invasive bryozoan M. membranacea, non-encrusted kelp, or starved. Data for each replicate container include diet, egg mass count, and number of snails per container.egg_production_data_lacuna.csvSnail survival data from: Invasive bryozoan alters interaction between a native grazer and its algal food. A Canadian Healthy Oceans Network Ecosystem Function Project, EF-11.Survival of snails (Lacuna vincta) maintained in feeding arenas in the laboratory over 4 weeks on single diets of either kelp (Saccharina latissima) encrusted by the invasive bryozoan M. membranacea, non-encrusted kelp, or starved. Data for each replicate container include diet and proportion of snails surviving at start of experiment and by the end of weeks 1-4.survival_data_lacuna.csv