The dataset includes nitrogen and phosphorus excretion rate
estimates from eight research programs and spans observations from
1999 to 2023. The appropriate datasets were identified during the
2022 LTER All-Scientists Meeting in Monterey, California. For
information on dataset provenance, please see the Data Source
section below. Datasets assessed for inclusion in working group
efforts required size measurements (i.e., either mass or length)
at the individual species level, alongside animal density
estimates (# per unit area), in order to estimate nitrogen and
phosphorus excretion rates using universal models published by
Vanni & McIntyre (2016). These models required the following
information to estimate excretion for individual animals: (1)
individual dry biomass, (2) temperature, (3)
vertebrate-invertebrate classification, and (4) coarse trophic
guild categorization. For projects that recorded individual
biomass but had missing values (i.e., due to field or data entry
errors), we calculated the average mass for the given species
within the program to estimate individual mass. For datasets that
had length but no mass measurements, mass was calculated using
length-weight coefficients published on FishBase or SeaLifeBase.
Dry biomass was calculated for all individuals using project-level
coefficients. In cases where wet-dry biomass coefficients were not
available at the site, published coefficients were used to convert
wet to dry mass. Temperature was held constant across each of the
projects using mean water (for aquatic organisms) or air (for
terrestrial organisms) temperature during the sampling period,
using environmental data from the respective projects. Taxonomic
classifications were determined using the taxize package in R, and
the information was used to determine whether vertebrate or
invertebrate coefficients were to be used in excretion rate
calculations. Individual species were assigned to one of five
trophic guilds (i.e., algivore/detritivore, invertivore,
piscivore, piscivore/invertivore, and
algivore/detritivore/insectivore/piscivore). The trophic guild of
individual species was determined by project experts from each of
the respective research programs. Once individual datasets
contained the necessary information for excretion rate
calculations, we performed zero-filled to permit calculation of
areal excretion rate estimates for nitrogen and phosphorus in the
unit of μg/m^2/hr. Next, standard column names were assigned to
individual dataset in the data integration process.
Sampling method for each program:
FCE
Florida Coastal Everglades LTER (FCE) is a subtropical estuary in
southwest Florida, USA. FCE has collected fish community data
since 2004. Sampling occurs throughout the year at 15 fixed sites
across the upper Shark River and Tarpon Bay, a large shallow
estuarine bay. Three primary sampling events occur at the end of
the wet season when water levels are at or near peak (i.e.,
November or December), during transitional periods when water
levels are intermediate (i.e., February or March), and when water
levels are at or near lows (i.e., April, May, or June). Fish are
sampled using standardized electrofishing along three 100 m
transects at each of the sites resulting in a total of 45
transects shocked during primary sampling events. Additional
monthly samples are collected during the dry season during months
not covered by the primary sampling at a subset
(n = 5) of sites in the upper river to
monitor inter- and intra-annual variability in community
composition at the marsh-mangrove interface as marsh taxa seek
refuge from desiccation as a result of falling water levels in
adjacent marsh habitats, and estuarine taxa track the resulting
prey subsidy. Collected fish are identified to species, measured
(i.e., length to nearest mm and weight to nearest mg), and
released at the approximate point of capture. An extreme cold
event in South Florida during January 2010 caused mass mortality
in tropical fishes and shifted community structure (Boucek et al.,
2013). In September 2017, Hurricane Irma brought devastating wind,
rain, and storm surge to FCE as the eye passed within 60 km of
Shark River (Massie et al. 2019). The storm had major impacts on
the distribution and movement of several large-bodied estuarine
consumers across the estuary. Further, extreme drought events in
2010 and 2015 had large effects on community structure and biomass
as a result of greatly diminished production in adjacent marsh
habitats (Boucek et al., 2013; Boucek et al., 2016).
PISCO
The Partnership for Interdisciplinary Studies of Coastal Oceans
(PISCO) conducts long-term and large-scale studies to understand
the functioning of the coastal marine ecosystem along the U.S.
west coast, focused on the biological and oceanographic drivers of
rocky intertidal and kelp forest ecosystems. Here we focus on kelp
forest and rocky reef fishes in central and southern California
(Malone et al. 2021). Surveys are conducted annually, generally
from June to late October from 1999 through present. To
comprehensively and quantitatively characterize the ecological
community and geological features at each kelp forest site, five
different sampling methods are employed, all of which are
conducted visually by SCUBA divers. Sites are surveyed for fishes
and benthic organisms separately, with differing transect
replication for the two methods. Transects are laid in a
stratified random design with non-fixed transects at specified
locations (sites) and targeted depth zones. The number and
arrangement of these zones depends on the width and slope of the
rocky reef at each site. Fish transects and benthic macroalgae and
invertebrate transects overlap with, but are spatially distinct
from one another.
The density of all conspicuous fishes (i.e., species whose adults
are longer than 10 cm and visually detectable by SCUBA divers) are
visually recorded along replicate 2m wide by 2m tall by 30m long
transects. In pairs, one diver surveys this volume along the reef
surface (searching within cracks and crevices), while other
surveys the same volume roughly one third to one half up into the
water column (i.e., “mid-water”) above the benthic diver,
depending on visibility and bottom depth. Canopy transects of the
same dimensions as the mid-water and bottom transects are surveyed
at a subset of sites, mainly to target juvenile fish recruiting to
the kelp canopy. Canopy transects are only done where kelp canopy
extends to the surface and are usually completed separately from
the bottom and midwater transects. Typically, for each portion of
the water column sampled, three 30m long transects are distributed
end-to-end and 5-10m apart at each of the 5m, 10m, 15m, and 20m
isobaths. At sites with narrow kelp beds, particularly in parts of
the Northern Channel Islands, only two zones are sampled, with
four transects in each depth zone for a total of eight replicate
transects. Counts on mid-water and bottom transects are eventually
combined, thereby generating 8-12 replicate transects for each
site for analyses. Fish transects are generally only conducted
with at least 3m of horizontal visibility. The total length (TL)
of each fish observed is estimated to the closest 1cm. For each
transect, divers record the transect depth, horizontal visibility
along each transect, water temperature, and sea state (surge), and
percent of the transect volume occupied by kelp.
SBC
The Santa Barbara Coastal LTER (SBC) consists of nearshore rocky
reefs dominated by giant kelp (Macrocystis
pyrifera) and sandy beaches in the Santa Barbara
Channel, California, USA. SBC’s focus is on understanding the
ecology of nearshore kelp forests and their connectivity to
adjacent coastal ecosystems. Giant kelp, as a foundation species,
facilitate high biodiversity and abundance of sessile and mobile
invertebrates as well as numerous fish and elasmobranch species
(Millers et al. 2018). Annual kelp forest biodiversity monitoring
began in 2000 and consists of diver surveys of benthic
invertebrate and fish at 11 study sites in replicate, fixed 40 m
by 2 m transects (See the data source for SBC dataset). Along each
transect, divers count and estimate size of organisms within each
transect. Fish surveys are restricted to two meters above the
bottom. Species-specific biomass values are estimated from size
measurements using allometric relationships (Nelson et al. 2021).
Export of giant kelp NPP to adjacent sandy beach ecosystems serves
as the base of the food web for this ecosystem which has little to
no in situ primary production. SBC began
conducting regular surveys at two sandy beach sites in 2013 (~
every six to eight weeks) of kelp wrack consumer (beach hoppers,
Megalorchestia spp.) populations. Sediment
cores (n = 10) are collected along three
replicate transects, sieved, and frozen. In the laboratory,
samples are sorted to species level, counted, and weighed to the
nearest mg (wet weight). To test the sensitivity of our universal
excretion estimates, we compared them to empirical excretion data
for kelp forest benthic invertebrates (Peters et al. 2019) and
sandy beach invertebrates (Lowman et al. 2019).
CCE
The California Current Ecosystem (CCE) LTER is a pelagic eastern
boundary current upwelling biome (32.8736, -120.28) along the
California, USA coast. The site was established in 2004, building
upon the historic California Cooperative Oceanic Fisheries
Investigations (CalCOFI) time series (1949–present). Biological
and hydrographic data are collected by both CalCOFI (quarterly)
and the CCE-LTER program (every 2-3 years). The CalCOFI sampling
grid consists of 6 lines extending from onshore to offshore, with
onshore stations spaced 20 nautical miles (nm) and offshore spaced
40 nm apart. From the grid, Line 80 and Line 90 are sampled for
mesozooplankton analysis. Mesozooplankton (>0.2 mm) were
collected during quarterly CalCOFI cruises (2005–present) using a
50 cm diameter, 202 µm mesh, 3 m length PRPOOS (Planktonic Rate
Processes in Oligotrophic Ocean Systems) Net. The net collects an
integrated zooplankton community down to 210 m depth (using a
descent rate of 40 m/min, held at depth for 20 sec, and then an
ascent rate of 50 m/min). Upon collection, zooplankton are
preserved in formaldehyde and maintained in the Scripps
Institution of Oceanography Pelagic Invertebrate Collection.
Zooplankton samples preserved in formaldehyde were imaged using a
Zoooscan (Gorsky et al., 2010). Measurements
of abundance (individuals/m2) estimated
carbon biomass (mgC/m2), ferret
diameter (mm), and individual carbon content (µg/individual) were
downloaded from Zooscan Database on January 24th, 2024 for
appendicularians, bryozoan larvae, chaetognaths, calanoid
copepods, eucalanid copepods, harpacticoid copepods, oithona-like
copepods, poecilostomatoid copepods, other copepods, other
crustaceans, doliolids, euphausiids, ostracods, polychaetes,
pteropods, pyrosomes, rhizarians, and salps. Measurements of
individual carbon content (were transformed into dry mass
(g/individual) to compare to other sites biomass data, using
conversations rates in literature (Brey et al. 1988; Mansour et
al. 2021; Uye 1982; Larson 1986).
MCR
The Moorea Coral Reef LTER (MCR-LTER) is a tropical coral reef
ecosystem in Moorea, French Polynesia (17°30 S, 149°50 W), located
in the central South Pacific. Since 2005, the MCR-LTER has
conducted ongoing fish surveys as a part of the MCR-LTER fish
monitoring program. Annual fish surveys are conducted during the
dry season from late July to early August between 0900 and 1600
hours (local time) on SCUBA. Fish are counted at 4 replicate
transects 50m in length, across coral reef types. The island of
Moorea has three distinct sides North, Southeast and Southwest.
Fish are surveyed on all three sides of the island at two
locations on the fringing reef, backreef and forereef for a total
of 72 individual surveys. Annual fish surveys conducted on the
fringing reef, back reef and fore reef are completed at a depth of
1.5m, 10m and 12m, respectively. To better estimate the fish
community and promote diver safety two divers perform the fish
survey using two swaths (one swath per diver). A 5m and 1m swaths
are used at each transect to count mobile fish and cryptic fish
species. However, prior to 2021 all fish surveys were completed by
a single diver on SCUBA using a 5m swath. For each transect,
species abundance and estimated sizes of fishes are recorded.
Additional data collected at each transect are wind, sea state,
swell height, cloud cover, and visibility.
From 2007-2009, a crown of thorns sea star outbreak
caused massed coral mortality events on the island of Moorea. This
outbreak affected sites across the island resulting in significant
coral mortality and shifts in the fish community (Adam et al
2014). In 2010, Moorea experienced a severe tropical cyclone event
that significantly decreased live coral cover at sites along the N
shore. This loss in coral structure had a large impact on fish
functional groups that depend on coral structure such as coral
dwellers and corallivores (Adam et al. 2014) In 2019, there was an
extreme heat wave that resulted in mass mortality of large coral
colonies (Speare et al. 2022).
NGA
Northern Gulf of Alaska (NGA LTER) research cruises conducted in
the Gulf of Alaska in 1997-2022. The data were collected to
determine the distribution, abundance and biomass of zooplankton
from traditional microscopy on samples obtained from a Multinet
samples and QuadNet. For Multinet sampling, a 0.25-m2 Hydrobios
Multinet system with 0.5 mm mesh nets were fished at night to
assess large zooplankton and micronekton such as euphausiids that
are important components in the diet of many fish, sea-birds and
marine mammals. Night-time collections are essential to collect
diel migrators and minimize avoids by higher-speed
visually-responsive species. The Multinet is equipped with five
nets that can be programmed to open and close at specific depths,
or opened and closed electronically from the deck if a conducting
cable is available. Depth, flow meter counts, and volume filtered
are recorded at 1 second intervals. Prior to 2018, at each
station, 5 samples were collected at 20 m depth intervals from 100
m depth to the surface. Starting in 2018, stratified were modified
to 200-100-60-40-20-0 m. All zooplankton samples were preserved in
10% formalin for later analysis by microscopy to the lowest
taxonomic category possible. For QuadNet, Day-time zooplankton
samples were collected with a Quadnet consisting of two 25 cm
diameter, 150 um mesh nets and two 25 cm diameter, 53 um mesh nets
(all aspect ratios 10:1) equipped with General Oceanics flowmeters
that were towed vertically through the water column from a target
depth of 100 meters to the surface. All samples were immediately
preserved in 10% formalin for later analysis.
The zooplankton samples were processed as follows: Each sample was
poured into a sorting tray and large organisms, primarily shrimp
and jelly fish, were removed and enumerated. The sample was then
sequentially split using a Folsom splitter until the smallest
subsample contained about 100 specimens of the most abundant taxa.
The individual organisms were identified and measured using a
microscope and a digitizing tablet. Each larger subsample was
examined to identify and enumerate the larger, less abundant taxa,
while ceasing to consider those adequately enumerated in prior
subsamples. Abundance was calculated from the counts of each taxon
in the sample fraction divided by the volume of water filtered by
the net. Wet weights were calculated from existing in-house
length-weight equations, or where they did not exist, from direct
weights.
Data Source:
Florida Coastal Everglades:
https://pasta.lternet.edu/package/data/eml/knb-lter-fce/1164/12/de8a81c56378979f369fff30bbde9f01
Moorea Coral Reef:
https://doi.org/10.6073/pasta/75644add7e7f90c568bf5045264d359a
Plum Island Ecosystems:
https://doi.org/10.6073/pasta/de6b4cbb10fa240a63c95ffdd6152432
Santa Barbara Coastal (ocean):
https://doi.org/10.6073/pasta/9ddf2268b69115670be27cdfd29ad104
Santa Barbara Coastal (beach):
https://doi.org/10.6073/pasta/d84164f4099a98817e3f0afa49546b94
Virginia Coast Reserve:
https://portal.edirepository.org/nis/mapbrowse?packageid=knb-lter-vcr.236.14
The Partnership for Interdisciplinary Science of Coastal Oceans
(PISCO): https://doi.org/10.25494/P6/MLPA_kelpforest.5
California Current Ecosystem:
https://oceaninformatics.ucsd.edu/zooscandb/secure/login.php
Plankton sample analysis supported by NSF grants to M.D. Ohman,
Scripps Institution of Oceanography and by the CCE-LTER site.
Northern Gulf of Alaska (The data from 2018-2021 were published on
DataOne):
Russell Hopcroft. (2021). Zooplankton abundance and biomass
observations obtained from the QuadNet, as analyzed by traditional
microscopy, during NGA LTER seasonal cruises in the Northern Gulf
of Alaska, 2018-2021. Research Workspace. 10.24431/rw1k587,
version: 10.24431_rw1k587_20230930T230143Z.
Russell Hopcroft. (2021). Zooplankton abundance and biomass
observations determined traditional microscopy, from Multinet
samples collected during research cruises for the Northern Gulf of
Alaska LTER site, 2018-2021. Research Workspace. 10.24431/rw1k591,
version: 10.24431_rw1k591_20230930T225433Z.
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