1 research outputs found
Year IV of Post Restoration Monitoring at Shiawassee National Wildlife Refuge
Our research took place at Shiawassee National Wildlife Refuge (SNWR) where recent
hydrologic reconnection has restored a large area of floodplain wetland in the Shiawassee Flats
region, where four major rivers meet before flowing into the Saginaw Bay. In this fourth and
final year of post-restoration monitoring, our project team sought to assess the ecological health
of the recently restored wetlands in comparison to reference conditions and previous years.
Through a partnership with the U.S. Fish and Wildlife Service and U.S. Geological Survey, we
were able to effectively carry out four months of ecological research monitoring centered around
the study of four indicators of overall wetland health: water quality, vegetation, aquatic
macroinvertebrates, and fish.
Our goals for 2022 were to evaluate ecological conditions indicative of the wetland’s overall
ecosystem health shortly after restoration in order to demonstrate the impact and value of
SNWR’s restoration investment. By collecting and analyzing a robust set of ecological data
along with comparing conditions across years, our team is able to provide recommendations to
refuge managers and provide the data to support this refuge’s standing as a wetland restoration
model for the Great Lakes region.
Water Quality: We analyzed five key water quality parameters: average temperature, average pH,
average conductivity, average turbidity, and average dissolved oxygen, for variation across
months, wetland management unit, and vegetation type. Additionally, we analyzed nutrient
samples to characterize the relationship between turbidity and dissolved Nitrogen and
Phosphorus concentrations throughout SNWR. Finally, we visually compared water quality and
nutrient levels across all four years of post-restoration monitoring.
● We found consistent trends in water quality across 2019-2022; conductivity is higher in
the Shiawassee River (SHR) and Pool 1A (P1A) than in Maankiki units, and Maankiki
South (MS) consistently holds the lowest dissolved oxygen levels.
● In 2022, water quality varied significantly across season, management unit, and
vegetation type which in turn impacts community assemblages and seasonal movements
of invertebrates and fish which impact higher trophic levels.
● Dissolved oxygen (DO) is possibly the most salient determinant of species guilds among
our five parameters and limits the range of more sensitive taxa within the refuge making
preservation of areas of higher DO important to preserving overall species diversity.
● We found a significant correlation between pH and dissolved oxygen which is related to
rates of autotrophy and heterotrophy.
2
● Turbidity still cannot be used as a reliable predictor for Phosphorus and Nitrogen
concentrations, but in the future, using flow data as another predictor variable may help
elucidate the relationship between Lake Huron seiche dynamics and upstream nutrient
levels, or conversely the impact of upstream river water on nutrients at SNWR.
● Recommendations for management include increased sampling of water quality in certain
vegetation types to better assess spatial heterogeneity, incorporating flow data into
nutrient analysis, as well as preserving areas of high dissolved oxygen that are correlated
with specific vegetation types.
Vegetation: We surveyed and identified the plant community at SNWR with the goal of
describing the vegetative structure of each of the four wetland management units, as well as the
overall ecological health of the vegetative community within the sampled area. We performed
190 individual quadrat samples, collecting between 35 and 55 sample points in each wetland
management unit, and performed a variety of statistical analyses in order to compare and contrast
biotic indices in the wetland management units amongst dominant vegetation zones, individual
units, and among overall sampling years (2019-2021). We found that:
● The ecological health of SNWR’s 4 wetland management units, while relatively low
when compared with pristine pre-colonial reference conditions, is fairly high in the
context of regional wetland quality.
● Indices of Biotic Integrity (IBI) scores have decreased since 2021 as a result of
interannual discrepancies in data analysis and interpretation.
● Maankiki Center (MC), the most recently connected wetland management unit, had the
lowest IBI assessment, and its 2022 metrics differed greatly from analysis performed in
2021.
● Floristic Quality Analysis (FQA) and Floristic Quality Index (FQI) scores have increased
in every unit since the 2021 sampling season.
● Based on our data and results, we provide future recommendations for the management
՟of these wetland management units, including the prioritization of invasive species
management via removal and intentional flooding.
Aquatic Macroinvertebrates: We describe variations in macroinvertebrate abundance and
community composition in SNWR and compare our findings to previous monitoring seasons,
2019-2021. Data is analyzed by unit, month, and vegetation zones of sampling.
● We collected macroinvertebrates from 55 sites and obtained fewer total individuals than
previous years but maintained similar taxa richness.
3
● The month of sampling contributed to the total abundance of macroinvertebrates
collected, likely due to seasonal changes in the environment that trigger transitions in
life-cycle stage.
● P1A, the ‘reference’ unit, had a community composition different than that of the
Maankiki Marsh units, which is likely attributable to invertebrate dispersal ability and
time-since-reconnection (as it is the oldest restored unit).
● Vegetation type had little impact on macroinvertebrate abundance or composition across
all units.
● When calculating macroinvertebrate IBIs, all wetland management units were
considered “mildly impacted.” This represents an increase in IBI values from the
previous sampling season (2021).
Fish: We monitored and surveyed wetland management units to characterize how fish
populations are influenced by seasonal variation and interaction of other biotic and abiotic
factors. Our research goals include assessing wetland health with IBI scores across wetland
management units over the months of May, June, July, August, and October of 2022. Two gear
types, fyke netting and electrofishing, were used to sample a wide variety of habitats within the
wetlands, spanning various vegetation zones and water depths. There were a total of 108 fyke
nets set and 31 electrofishing sites surveyed during the summer 2022 field season. We conducted
statistical analysis to determine the implications of the data collected from monitoring. Statistical
analysis allowed for an in-depth look at fish species abundance, community composition, and an
assessment of the ecological wetland health.
● Despite dynamic filters that constrain the species pools of SNWR, the restored wetlands
have recovered relatively quickly.
● The most recently restored wetland management unit, MC, is still more similar to SHR
showing that there is a stage of colonization where species must compete to establish in
the previously inaccessible habitat.
● IBI score assesses overall health of wetland management units based on species
composition which ranged from moderately impacted (>45-50) to degraded (<36). Over
the past four years, fish IBI has generally improved in the wetland management units.
● We surmise that the high fish abundance and various assemblages that we found support
complex trophic interactions and high-quality ecosystem services. Trophic interactions
between vegetation and macroinvertebrates are important factors in determining species
composition and abundance.
● Island biogeography theory plays an important role in understanding the importance of
unit connectivity and explains ecological variation by collective time of unit connection.
4
In the final year of post-restoration monitoring, our team was able to incorporate past years’ data
alongside data from 2022 to comprehensively characterize ecological conditions shortly after
restoration. Overall, our findings suggest a successful response of biotic communities to
hydrologic reconnection and enable us to make recommendations that support further habitat
improvements and biodiversity.Master of ScienceSchool for Environment and SustainabilityUniversity of Michiganhttp://deepblue.lib.umich.edu/bitstream/2027.42/176162/1/SHIA-IV_MP_2023.pd