Abundance Biomass Research Articles

No effect of nearby natural reef existence on fish assemblages at shipwrecks in the Aegean Sea

AbstractDeployment of artificial wreck reefs (AWRs) near natural reefs can influence fish assemblages on both reefs. Here, we assessed fish attitudes (abundances, biomass and species richness) according to different level complexity areas of wrecks, feeding guilds of fish and body size of fish of two identical AWRs deployed at the same depth (36.6 m) and different distances from natural reefs. Scuba divers used visual census method to sample fish communities at wrecks for two years. An average of 2346 individuals per dive belonging to 52 species were observed on wrecks combined. Both mean fish abundance and mean biomass did not differ significantly between wrecks. Mean species richness was significantly greater at9 EylülthanAlaybey. Planktivore was the most abundant feeding guild on wrecks, and its abundance statistically differed between AWRs. The comparisons of fish assemblages at the different level complexity areas of the wrecks show differences, the highest mean abundances were recorded at the areas of low complexity of the wrecks. The results of this study show that although deploying artificial wreck reefs near to natural rocky reefs catalyses fish colonization, it does not present an exact influence on the fish communities of AWRs. We have not known yet how creating an artificial wreck reef affects fish community of natural reefs. With giving extra importance to the choice of deployment area, AWR applications may transform to win-win projects for both the marine environment and recreational users, such as divers and anglers.

A simple metric for predicting the timing of river phytoplankton blooms

AbstractIn rivers, phytoplankton populations are continuously exported by unidirectional, advective flow. Both transport and growth conditions determine periods of excess phytoplankton growth, or blooms, in a given reach. Phytoplankton abundance, however, has mainly been compared to the state of either growth or transport conditions alone rather than in tandem. Previous studies have not yielded consistent driver–response relationships, limiting our ability to predict the timing of riverine phytoplankton blooms based on environmental factors. Here, we derive a simple joint metric that combines the state of growth and transport conditions, specifically the ratio of temperature and discharge (). We then compare the metric to biomass abundance data (daily, sensor‐based chlorophyll a [chl a] data) from a mid‐sized Great Plains river (the Kansas). was an excellent predictor of low to high biomass, outperforming either variable alone. However, it could not differentiate between very high biomass values, values well above the biomass threshold designating bloom conditions. Our findings of reduced performance at the highest values of T/Q indicated that could predict the occurrence (timing) but not magnitude of phytoplankton blooms, and we used T/Q to correctly predict 71% of days when bloom conditions occurred. Analyzing chl a abundance with also revealed likely switching from transport and temperature to nutrient control. offers a simple tool for (1) predicting the timing of river phytoplankton blooms, (2) forecasting how river ecosystems will respond to surrounding environmental changes, and (3) determining which environmental factors shape phytoplankton blooms at specific locations along a river.

High seed diversity and availability increase rodent community stability under human disturbance and climate variation.

The relationship between diversity and stability is a focus in community ecology, but the relevant hypotheses have not been rigorously tested at trophic and network levels due to a lack of long-term data of species interactions. Here, by using seed tagging and infrared camera tracking methods, we qualified the seed-rodent interactions, and analyzed the associations of rodent community stability with species diversity, species abundance, and seed-rodent network complexity of 15 patches in a subtropical forest from 2013 to 2021.A total of 47,400 seeds were released, 1,467 rodents were marked, and 110 seed-rodent networks were reconstructed to estimate species richness, species abundance, and seed-rodent network metrics. We found, from younger to older stands, species richness and abundance (biomass) of seeds increased, while those of rodents decreased, leading to a seed-rodent network with higher nestedness, linkage density, and generality in older stands, but higher connectance in younger stands. With the increase of temperature and precipitation, seed abundance (biomass), rodent abundance, and the growth rate of rodent abundance increased significantly. We found rodent community stability (i.e., the inverse of rodent abundance variability) was significantly and positively associated with seed diversity, seed availability, linkage density and generality of seed-rodent networks, providing evidence of supporting the Bottom-Up Diversity-Stability Hypotheses and the Abundant Food Diversity-Stability Hypothesis. Our findings highlight the significant role of resource diversity and availability in promoting consumers' community stability at trophic and network levels, and the necessity of protecting biodiversity for increasing ecosystem stability under human disturbance and climate variation.

What is the role of disturbance in catalyzing spatial shifts in forest composition and tree species biomass under climate change?

Mounting evidence suggests that climate change will cause shifts of tree species range and abundance (biomass). Abundance changes under climate change are likely to occur prior to a detectable range shift. Disturbances are expected to directly affect tree species abundance and composition, and could profoundly influence tree species spatial distribution within a geographical region. However, how multiple disturbance regimes will interact with changing climate to alter the spatial distribution of species abundance remains unclear. We simulated such forest demographic processes using a forest landscape succession and disturbance model (LANDIS-II) parameterized with forest inventory data in the northeastern United States. Our study incorporated climate change under a high-emission future and disturbance regimes varying with gradients of intensities and spatial extents. The results suggest that disturbances catalyze changes in tree species abundance and composition under a changing climate, but the effects of disturbances differ by intensity and extent. Moderate disturbances and large extent disturbances have limited effects, while high-intensity disturbances accelerate changes by removing cohorts of mid- and late-successional species, creating opportunities for early-successional species. High-intensity disturbances result in the northern movement of early-successional species and the southern movement of late-successional species abundances. Our study is among the first to systematically investigate how disturbance extent and intensity interact to determine the spatial distribution of changes in species abundance and forest composition.

Testing the suitability of the abundance biomass comparison bioassessment method in a Mediterranean river

The Water Framework Directive (Directive 2000/60/EC) emphasises the need for simple tools and studies to characterise aquatic ecosystems. A wide range of methods has been developed, including different groups of biota and different taxonomic resolutions. Among these, the abundance biomass comparison (ABC) method is an important methodology widely used in marine benthic systems and well-founded from the ecological point of view. This method – with a slight modification using genera and families instead of species – was applied in a Mediterranean river (Eliche-Frío, northeast of Andalusia, Spain) using the macroinvertebrate community, together with the Margalef richness index and the Iberian BioMonitoring Working Party ( IBMWP) to determine the quality of the water. The obtained results show the suitability of the ABC curves method to analyse the macroinvertebrate community and estimate the ecological status of river ecosystems. Although both, the genus and family aggregations, showed a similar trend, the values obtained with the family level indicate a worse state of contamination than those shown with the genus level. The comparison between genus and family levels with other biological indices shows that the evaluation obtained with family aggregation is more similar to those obtained with the Margalef and IBMWP indices than the evaluation based on genera; therefore, we could conclude that this level of taxonomic resolution is adequate for the use of the ABC method in assessing the ecological status of Mediterranean rivers.

Bt‐maize in neotropical arthropod food webs: community‐stress or lack thereof?

AbstractAlthough the agricultural use of genetically engineered (GE) plants has been employed extensively, its adoption is still controversial and its impact on arthropods has rarely been scrutinized at the community level. If this technology is aimed at a drastic reduction of a key community component, significant community‐level impact is expected and needs to be assessed. Thus, food web analysis was used to assess the short‐term impact of genetically modified maize plants, Zea mays L. (Poaceae), expressing insecticidal proteins of the bacterium Bacillus thuringiensis Berliner (i.e., Bt maize), on the associated arthropod assemblage in a neotropical scenario. Arthropods associated with winter and summer cultivations with Bt and non‐Bt (isoline) maize were thus sampled using sweep nets and whole‐plant collections throughout the plant phenological cycle. The collected information was used to build a plant‐consumer‐predator trivariate network based on data of individual arthropod body mass, numerical abundance, and biomass abundance using food web analysis. Eighty‐five arthropod species were sampled, and whereas cultivation season significantly affected arthropod species richness and abundance, only marginal differences existed between maize hybrids (Bt vs. non‐Bt). The recognized food webs also indicated significant differences between seasons. In contrast, Bt‐maize‐hosted food webs were similar to those of the non‐Bt isoline indicating no significant impact on arthropod food webs. Nonetheless, Bt maize did not provide significant control of the target pest species, the fall armyworm, nor did it lead to higher crop yield, raising questions about its current usefulness in the region.

Future Hurricanes Will Increase Palm Abundance and Decrease Aboveground Biomass in a Tropical Forest

AbstractHurricanes are expected to intensify throughout the 21st century, yet the impact of frequent major hurricanes on tropical ecosystems remains unknown. To investigate tropical forest damage and recovery under different hurricane regimes, we generate a suite of scenarios based on Coupled Model Intercomparison Project Phase 6 climate projections and increased hurricane recurrence and intensity for the Luquillo Experimental Forest, Puerto Rico. We then use the Ecosystem Demography model to predict changes in carbon stocks, forest structure and composition. Our results indicate that frequent hurricane disturbances in the future would decrease the overall aboveground biomass, decrease the dominance of late‐successional species, but increase the dominance of palm species. Warmer climates with increased CO2 would have little effect on the functional‐type composition but increase the aboveground biomass. However, the predicted climate and CO2 fertilization effects would not compensate for the biomass loss due to more frequent severe‐hurricane disturbances.

Oceanographic conditions and analysis of walleye pollock <i>Theragra chalcogramma</i> fishery in the Navarin area in 2017–2021

The northwestern Bering Sea, in particular the waters at Cape Navarin, is one of the main areas of the walleye pollock fishery. Environmental variability in the Bering Sea affects on recruitment, abundance, behavior, and seasonal spatial distribution of pollock, which challenge on the fishery management strategy. Understanding of environmental-driven changes in the pollock population has to improve predictions of the population dynamics and affect positively on the commercial harvest. The pollock from the eastern Bering Sea migrate to the Navarin area in summer-fall season. This study demonstrates that great annual differences in the migration activity, spatial distribution of pollock and fishery are related with oceanographic conditions, zooplankton productivity, the population reproduction, year-classes abundance and total biomass. Appearance of the relatively abundant year-classes in 2017–2020 may lead to some increase in commercial part of the pollock population in 2022–2024.

Chlorophyll-a in Chesapeake Bay based on VIIRS satellite data: Spatiotemporal variability and prediction with machine learning

Chlorophyll-a (Chl-a) concentration indicates the abundance of phytoplankton biomass and its spatiotemporal variations fundamentally modulate the ecosystem dynamics in coastal waters. Compared to conventional low-frequency shipboard measurements at a limited number of sampling locations, satellite data provide a better spatial and temporal coverage allowing for a more synoptic view of Chl-a variabilities in large coastal systems such as Chesapeake Bay. We used Visible Infrared Imaging Radiometer Suite (VIIRS) satellite data from 2011 to 2018 to (1) analyze the Chl-a variability in Chesapeake Bay, (2) examine the robustness of an interpolation method to fill up satellite data gaps, and (3) train a machine-learning-based data-driven model to simulate high-resolution Chl-a variations. The dataset shows clear seasonality with notable spring and summer peaks throughout the bay; this is different from in situ observations at mainstem stations where the water is deep. The seasonality of Chl-a varies in different regions, with maxima concentration occurring in spring for regions near the mouths of major tributaries, winter near the bay entrance, and summer elsewhere. A machine-learning-based data-driven model, together with Data Interpolating Empirical Orthogonal Functions (DINEOF), is applied to simulate the high-resolution Chl-a variations. The DINEOF is used to efficiently estimate the missing records. Driven by external forcing including river discharge, nutrient loadings, solar radiation, wind, and air temperature, the data-driven model shows an overall satisfactory performance in reproducing the spatiotemporal variations of Chl-a, with a bay-wide averaged root mean square error of 1.85 ug/l. By combining DINEOF and machine learning, this study demonstrates the potential of using data-driven model to predict high-resolution spatiotemporal variations of water quality in coastal waters.

Effectiveness of Biomass/Abundance Comparison (ABC) Models in Assessing the Response of Hyporheic Assemblages to Ammonium Contamination

Abundance–Biomass Comparison (ABC) models, first described for marine benthic macrofauna, have been applied successfully to other marine and terrestrial/freshwater fauna but never to ecotonal communities. In particular, to our knowledge, ABC models have not been applied to hyporheic communities. This study represents the first application of ABC models to hyporheic assemblages. We aimed at testing the effectiveness of ABC models in describing the perturbation of hyporheic communities subjected to an existing/known disturbance. To this end, we applied the models to the hyporheic community of an Apennine creek, where the hyporheic waters of the upstream stretch were uncontaminated, whereas those of the downstream stretch were contaminated by ammonium. We also tested separated models for the summer and winter periods to account for potential variability due to season. ABC models provided a satisfactory description of the hyporheic community changes due to ammonium by showing the abundance dominance curve overlying that of the biomass in the downstream stretch contrarily to what was observed in the upstream stretch. However, ABC models did not highlight any significant seasonal effects. Our results showed that ABC models have the potential to be used as assessment tools for ecological quality of hyporheic zones in temperate regions.

Expansion of Field Margin Size Mitigate the Hazard of Rotary Tillage to Earthworm in Rice-Rape Rotation System

Field margin (FM) provides refuges for earthworm survival in rape-rice system after flooding, while the effects of FM with different size on earthworm in arable field (AF) is unclear. In this study, we investigated the effects of different FM sizes, a conventional size (FM I) and three expanding sizes (FM II, FM III, FM IV), on earthworm population characteristics in FM and AF. The results showed that the mean abundance of earthworm under the expanding sizes at 1 day and 60 day of flooding after rape harvest was 16.5 and 20.2 times higher than that of FM I, respectively. After stopping flooding, juveniles first migrated from FM to AF, whereas more than half of them were killed by subsequent rotary tillage, and the mortality decreased with expanding FM size. Subsequently, expanding FM sizes promoted earthworm to distribute evenly through the AF at faster speeds. At rape maturity, the mean abundance and total biomass of earthworm of AF under expanding FM sizes were significantly greater than that of FM I, and this positive effect increased with expanding FM size. The results indicated that expanding FM size can mitigate the hazard of rotary tillage to earthworm and promote rapid recovery of earthworm population in AF.

Community structure and biomass of larval euphausiids and postlarval mysids in relation to anomalous warming events during a weekly time series (2014–2017) at Cabo Pulmo National Park, Mexico

Euphausiids and mysids are important components of pelagic ecosystems due to their high abundance and tendency to form dense aggregations, swarms, and schools, which concentrate biomass that attracts visual predators. Species richness, abundance, and carbon biomass of euphausiids and mysids were investigated from a weekly daytime surface zooplankton time series from 2014 to 2017, in relation to 15 environmental variables at Cabo Pulmo National Park (CPNP, 23°27′ N, 109°25′ W), Mexico. A marine heatwave (MHW; January–August 2014) and El Niño 2015–2016 (May 2015–May 2016) caused anomalously warm temperatures in relation to the 2002–2018 temperature time series. We tested the hypotheses that CPNP is dominated by a tropical euphausiid and mysid species assemblage and that abundance of both taxonomic groups decreased during the MHW 2014 and El Niño 2015–2016. Euphausiids (7.9 ind. m−3) had a higher mean abundance than mysids (3.4 ind. m−3). Eight euphausiid species, mostly of tropical-oceanic affinity, were collected (98 % larvae). Nyctiphanes simplex decreased and Euphausia distinguenda and Stylocheiron carinatum increased in abundance during El Niño 2015–2016. Five mysid species were collected (juveniles and adults). Mysidium rickettsi alone accounted for 99.98 % of total mysid abundance. Although the euphausiids collected were mainly larval stages, due to sampling in shallow coastal waters during the day, they contributed more biomass than juvenile and adult M. rickettsi in the pelagic habitat, though the abundance of this mysid in its epibenthonic habitat was likely underestimated. A canonical correspondence analysis of euphausiid and mysid abundance as a function of 10 environmental variables explained 77.4 % of the total variability, showing greater seasonal (warm vs cold) than interannual changes. The best correlated environmental variables with euphausiid and M. rickettsi abundance were net primary production (−0.419), zooplankton biovolume (0.3177) and the MEI.v2 (−0.278). We concluded that the most evident changes in community structure and abundance were seasonal (e.g. N. simplex dominated during the cold season while E. distinguenda dominated during the warm season) rather than interannual. Moreover, the abundance and biomass of euphausiids decreased during the MHW 2014 and El Niño 2015–2016; paradoxically the highest abundance and biomass of E. distinguenda and the mysid M. rickettsi occurred during El Niño 2015–2016. This implies higher available biomass for benthonic and nektonic predators in this neritic tropical reef ecosystem, contrasting with decreased abundance of euphausiids observed along the west coast of the Baja California Peninsula during this period.

Ecological interactions between Antarctic krill (Euphausia superba) and baleen whales in the South Sandwich Islands region – Exploring predator-prey biomass ratios

Following the cessation of whaling, the southwest Atlantic humpback whale (Megaptera novaeangliae) population is thought to be close to pre-exploitation size, reversing 20th century changes in abundance. Using a model-based approach applied to concurrently collected data on baleen whale abundance and Antarctic krill (Euphausia superba) biomass in the South Sandwich Islands (SSI) region, we explore ecological interactions between these taxa. Krill biomass and baleen whale density were highest to the north and northeast of the SSI, where the Antarctic Circumpolar Current (ACC) is deflected around the island chain. Humpback whale density was elevated at locations of krill biomass density >150 gm-2. Krill consumption by baleen whales was estimated at 19–29% of the available krill standing stock. We used historic whaling data to confirm the plausibility of these consumption rates and found evidence of rapid weight gain in humpback whales, such that blubber depleted during the breeding season could be restored in a much shorter period than previously assumed. Little is known about krill replenishment rates in the flow of the ACC, or about niche separation between recovering baleen whale populations; both factors may affect species carrying capacities and further monitoring will be required to inform the management of human activities in the region.

Grazing during the grassland greenup period promotes plant species richness in alpine grassland in winter pastures.

Although grazing is the most common use of grassland, the ecological function of grassland far exceeds its productivity. Therefore, the protection of plant diversity is of the utmost importance and cannot be ignored. Existing research on the effect of grazing on grassland mainly focuses on grazing intensity and the type of livestock, but the consequences of the timing of the grazing on the vegetation community remains unclear. We investigated plant community characteristics of winter pastures in alpine meadow with different grazing termination times (grazing before and during the grassland greenup periods) in Maqu County, eastern QTP. The results showed that vegetation height, coverage, aboveground biomass and Graminoid biomass were lower in grassland when grazing happened during the greenup period compared to grassland where grazing was terminated before the greenup period. However, the total plant species richness and forbs richness were higher in grassland with grazing during the greenup period compared to grassland without grazing during the greenup period. Our structural equation modeling reveals a potential indirect implication for the total plant species richness and forbs richness of winter pastures mainly through a decrease in the vegetation coverage and grass biomass abundance. Our findings imply that grazing during the grassland greenup period may facilitate the maintenance of plant diversity in winter pastures. These findings have important implications for grassland ecosystem functioning and for the conservation of plant diversity.

Inter-Annual Variability Of Spring And Summer Blooms In The Eastern Baltic Sea

Changes in environmental conditions may have an effect on the occurrence and intensity of phytoplankton blooms. However, few studies have been carried out on this subject, mainly due to the lack of long-term in situ observations. We study the inter-annual variability and phenology of spring and summer blooms in the eastern Baltic Sea using a physical-biological model. The one-dimensional NPZD model simulates the development of both blooms in the water column with realistic atmospheric forcing and initial conditions representative of the eastern Baltic Sea between 1990 and 2019. On average, the spring bloom started on day 85 ± 7, reached its maximum biomass on day 115 ± 6 and declined after day 144 ± 5. The summer bloom started on day 158 ± 5, had its maximum biomass on day 194 ± 9 and ended after day 237 ± 8. The results showed that the summer bloom occurs 9 days earlier and last 15 days longer over the 30-year simulation period, but changes in the phenology of the spring bloom were not statistically significant. There is strong evidence that warmer periods favor both blooms, but in different ways. Warmer periods caused spring blooms to peak earlier, while summer blooms reached higher abundance. Additionally, a higher energy gain by the ocean led to longer summer blooms of greater abundance and higher biomass maxima. Overall, summer blooms are more sensitive to changes in the environment than spring blooms, being therefore more vulnerable to changes generated by climate change in the Baltic Sea.

Study of Composition and Surface Morphology of Seaweed as Biosorbent: A Review

Heavy metal contamination is harmful to living creatures and deteriorate environment. Adsorption of heavy metal by biomass as adsorbent been the best alternative for heavy metal removal. Despite abundance of biomass as biosorbent, approach on adsorption by seaweed been studied because of its prominence benefits such as accessibility, minimal cost and ease of use. Some metal can be accumulated by seaweed without causing any hazardous by product. Thus, sorption of heavy metal by seaweed as biosorbent is studied. In this article, relationship between adsorption of heavy metal ions with composition and surface morphology of seaweeds are reviewed. Tables used to summarise the difference of composition and morphology of seaweed after treated with metal.

The combined effects of microplastics and the heavy metal cadmium on the marine periphytic ciliate Euplotes vannus

Microplastics could be grazed by marine organisms and possibly transferred to higher trophic levels along the microbial loop. Due to their size and capacity to concentrate heavy metals that trigger joint toxic effects, microplastics (MPs) have already become a severe threat to marine organisms. The detrimental effects of MPs on large marine organisms have been studied, but the combined toxicity of MPs and cadmium (Cd) on protozoan ciliates remains unclear. In the present study, we selected different diameters and concentrations of polystyrene microspheres (PS-MPs) and Cd2+ as model MPs and heavy metals to evaluate their single and combined effects on the periphytic marine ciliate Euplotes vannus in relation to carbon biomass and oxidative stress. The MPs were indeed ingested by Euplotes vannus and significantly reduced the abundance and carbon biomass of ciliate populations. Combined exposure to MPs and Cd2+ not only increased the bioaccumulation of Cd2+ in ciliates but also exacerbated the decrease in ciliate biomass by increasing oxidative stress and membrane damage. In comparison, the effects of nano-sized plastics (0.22 μm) were more harmful than those of micro-sized plastics (1.07 μm, 2.14 μm and 5.00 μm). A smaller size represents a higher potential for penetrating biological members and a stronger adsorption capacity for cadmium. These results provide new insight into the combined toxicity of microplastics and heavy metals on ciliated protozoa and lay a foundation for higher trophic levels and ecosystems.

Non-native fish assemblages display potential competitive advantages in two protected small and shallow lakes of northern Italy

The introduction and establishment of non-native fish species is a widespread phenomenon in freshwater ecosystems, including small and shallow lakes. However, these ecosystems are often not considered in conservation and ecological studies and a few information is available on their fish communities and the impacts of biological invasions. Here, standardized fish surveys (gillnetting and electrofishing) and stable isotopes analysis (SIA) of carbon and nitrogen (δ13C and δ15N) were combined to assess fish community composition, trophic structure and trophic diversity, and to characterize the interspecific trophic interactions (as isotopic niches and their relative asymmetric overlap) of the native and non-native species (NS and NNS, respectively) found in two protected small and shallow lakes, San Michele and Campagna (northern Italy). In San Michele, 92% of the fish caught were NNS and both the individual and biomass per unit effort were dominated by NNS, particularly by the invasive Lepomis gibbosus L. and Ictalurus punctatus (Rafinesque, 1818). In Campagna, 5.6% of the fish in the total catches belonged to NNS and the numeric and biomass abundances of the assemblage were dominated by the NS Alburnus alborella (Bonaparte, 1841). SIA revealed that NNS had greater trophic structure and were exploiting a wider range of resources (as per Layman metrics) and had a higher asymmetric overlap than NS assemblages in both lakes. This was also evident when species-specific isotopic ecology was considered, underlining that, in both lakes, NNS (particularly the NNS Ameiurus melas (Rafinesque, 1820)) may have a competitive advantage over NS in case of limiting resources. The results thus pointed to a worrying conservation status of these lakes that may mirror the condition of other Italian shallow and small lakes highlighting the need to implement management actions to preserve these valuable ecosystems.

Impact of environmental factors on phytoplankton composition and their marker pigments in the northern Adriatic Sea

Phytoplankton composition, abundance and carbon biomass were investigated at monthly intervals during 2006–2007 at a coastal site, “Acqua Alta” an oceanographic tower, in the northern Adriatic Sea. Results were compared with chlorophyll a concentrations of phytoplankton classes attributed by HPLC-CHEMTAX analysis. Changes in the taxonomic structure were associated with environmental parameters. The total carbon biomass of phytoplankton was positively correlated with the temperature and negatively correlated with silicate concentrations. Nutrient concentrations were higher in the winter–spring period than in the summer-autumn period. The highest carbon biomass and abundance of phytoplankton were observed during summer–autumn months. Diatoms were the group that had the highest contribution to the total carbon biomass during the sampling period. Small flagellates, which were the major contributors to the total cell counts were dominant during the summer period. There was a significant correlation between carbon biomass and CHEMTAX-derived Chl a values of diatoms and dinoflagellates. However, the total carbon biomass of phytoplankton was not correlated with Chl a, which seemed to be related to seasonal changes in the ratios of C:Chl a of all taxonomic classes. This ratio was higher during the summer-autumn period (73 ± 33) than during the winter–spring period (17 ± 20).

Match/Mismatch Between Phytoplankton and Crustacean Zooplankton Phenology in the Strait of Georgia, Canada

The Strait of Georgia, Canada, is an important region for numerous commercially and culturally important species (e.g., herring, salmon, and orcas), yet little is known about the links between lower trophic level (e.g. phytoplankton and zooplankton) phenology due to historical sampling gaps. Here, we present fourteen years (2003-2016) of data linking interannual variability in phytoplankton and zooplankton phenology in the Central Strait of Georgia, BC. Satellite-derived chlorophyll a (Chl a) data were used to calculate spring bloom dynamics (bloom initiation, bloom intensity, and bloom magnitude). Average spring bloom initiation occurred during the last week of March in the Central Strait of Georgia. Bloom initiation occurred in mid-to-late February/early March during “early” Chl a bloom years (2004, 2005, and 2015) whereas initiation did not occur until the end of April during “late” bloom years (2007, 2008). Spring Chl a bloom initiation was significantly correlated with the North Pacific Gyre Oscillation (NPGO; r = 0.75, p < 0.01) and spring sea surface temperature (SST; r = -0.70, p < 0.01); spring blooms occurred earlier during warm years. When all environmental variables were considered together, NPGO best explained variations in spring bloom initiation (Adj R2 = 0.53, p < 0.01) and bloom magnitude (Adj R2 = 0.57, p < 0.01), whereas stratification best explained variations in bloom intensity (Adj R2 = 0.38, p < 0.05). Early Chl a blooms were associated with high crustacean abundance (maximum of > 1000 ind m-3) but low biomass (37.5 mg m-3). Independent of the Chl a data, hierarchical cluster analysis revealed similar groupings of years for crustacean abundance data. Most notably, community composition in cluster Group 2 (2004, 2005, and 2015; early Chl a bloom years), was comprised of a higher proportion of small crustaceans (e.g. non-calanoid copepods) compared to the other cluster groups. To our knowledge, this study provides the first evidence linking early spring Chl a bloom timing to a shift in the crustacean community towards smaller taxa in response to multiple warm events in the Strait of Georgia. Our results show that early Chl a blooms may potentially result in a mismatch between phytoplankton and large energy-rich crustacean zooplankton, with lower abundances of the latter. In contrast, average Chl a bloom years were optimal for large-bodied euphausiids, whereas late Chl a blooms were a match for some crustaceans (e.g., medium calanoid copepods), but not others (e.g., large calanoid copepods and amphipods). We hypothesize that early bloom years may result in poorer feeding conditions for juvenile salmon and other predators in the region.