DOI: 10.5061/dryad.m63xsj4fs
title: Seasonal oxygen, temperature, chlorophyll, and zooplankton data – Portage Lake, MN

description: This dataset includes seasonal water quality and zooplankton data from
 Portage Lake in Hubbard County, Minnesota, USA, during 2023–2024. The
 dataset contains three components: (1) vertical profiles of temperature,
 dissolved oxygen, and chlorophyll a; (2) discrete chlorophyll a
 samples from 2 depths at lake center; and (3) zooplankton community data
 containing species-level counts. Water profiles were taken at the lake
 center using a YSI EXO2 sonde, and discrete water samples were collected
 from 0.5 m and 3–4 m depths at lake center. Chlorophyll a samples were
 filtered, frozen, extracted in the dark for 18 hours, and analyzed with a
 Turner Designs 10-AU fluorometer. Zooplankton were sampled at lake center
 by pooling three net tows per replicate. Zooplankton were preserved in
 ethanol and identified under a stereoscopic microscope at 7x-70x
 magnification using standard identification keys. At least 300 individuals
 were counted per sample. Abundance is reported as individuals per liter.
 Missing values are denoted as "NA." This dataset can be used in
 seasonal lake studies and to support the monitoring and management of
 seasonally-freezing, north temperate lakes.
description: # Seasonal oxygen, temperature, chlorophyll, and zooplankton data –
 Portage Lake, MN Dataset DOI:
 [10.5061/dryad.m63xsj4fs](10.5061/dryad.m63xsj4fs) ## Description of the
 data and file structure **Seasonal water quality and zooplankton data for
 Portage Lake, Hubbard County, MN, USA (2023-2024)** ### Files and
 variables #### File: #### **Portage_CTD.csv** **Description:** Complete
 water column measurements of dissolved oxygen, chlorophyll *a*, and
 temperature in Portage Lake, Hubbard County, MN, USA (2023-2024) #####
 Variables: * "*Oxygen_perc_sat*" : dissolved oxygen in percent
 saturation * "*Chlorophyll_a_ug_L*" : chlorophyll *a* in
 micrograms per liter, μg/L * "Temperature_C " : temperature in
 degrees Celcius, °C #### **Portage_discrete_chlorophyll.csv**
 **Description:** Discrete chlorophyll a measurements from 2 depths at lake
 center (surface: 0.5 m below surface; bottom: 3-4 m below surface).
 **Methodology:** Whole water, not sieved, filtered through 0.22 cellulose
 nitrate filters, folded, stored in 15 ml falcon tubes, wrapped in foil,
 frozen. All filters were soaked in 10 ml of 90% acetone for 18 hours,
 vortexed, and read via flourometry in the dark. Triplicate. #####
 Variables: * "*Lake*": Lake name * "*Date*": Date,
 month, and year sample collected * "*Year*": Year sample
 collected * "*Depth_m*": Depth at which sample was collected in
 meters * "*Replicate*" : replicate *
 "*Chl_mls_filtered"* : milliliters water filtered -
 "*Chl_raw_ug_L*" : raw fluorometer value in μg/L -
 "*Extracted_vol_mls"* : extracted volume in milliliters -
 "*Adjusted_fluorometer_value*" : adjusted fluorometer value
 in μg/L - "*Chl_ug_L*" : final chlorophyll a value in in μg/L
 #### **Portage_zooplankton.csv** **Description:** Zooplankton species data
 from tows taken at lake center from 1 m above lake bottom to surface. 
 **Methodology:** Triplicate samples for identification were preserved in
 70% ethanol. Each replicate consisted of three pooled net tows. Subsamples
 of each replicate were counted and identified under an Olympus SZH10
 stereoscope following Balcer et al. (1984). Adults were classified to
 species for copepods and cladocerans, while copepodites were grouped as
 cyclopoids or calanoids. Nauplii were counted without further
 classification. Individuals carrying egg sacs or brood pouches were also
 recorded. At least 300 individuals were identified per sample, and
 abundance was reported as individuals per liter (Ind. L⁻¹). If a sample
 showed a noticeably different abundance, it was recounted. Only one
 replicate for Jan 2023. ##### Variables: * "*Replicate*" :
 replicate. If a sample contained a noticeably different abundance than the
 other replicates, the sample was recounted. Recounted samples are noted as
 "recount" under "Replicate." *
 "*Tow_number"* : number of pooled tows per sample replicate -
 "*Sample_depth_m"* : sample depth in meters -
 "*Area_net_opening_cm*" : area of net opening in centimeters -
 "*Total_volume_ml"* : total volume of sample in milliliters -
 "*Volume_sorted_ml*" : total volume sorted in milliliters -
 "*Total_individuals_counted*": total individuals counted per
 sample - "*Total_Ind_L*": total individuals per liter per sample
 - Abundance of major zooplankton taxa are included as individuals per
 liter: Daphnia_mendotae_Ind_L, Daphnia_pulicaria_Ind_L, Daphnia_parvula_Ind_L, Daphnia_birgei_Ind_L, Daphnia_retrocurva_Ind_L, Daphnia_longiremis_Ind_L, Ceriodaphnia_dubia_Ind_L, Bosmina_longirostris_Ind_L, Chydous_sphaericus_Ind_L, Alona_Ind_L, Skidiaptomis_oregonensis_Ind_L, Leptodiaptomus_sicilis_Ind_L, Leptodiaptomus_minutus_Ind_L, Diacyclops_thomasi_Ind_L, Tropocyclops_prasinus_mexicanus_Ind_L, Acanthocyclops_vernalis_Ind_L, Eucyclops_agilis_Ind_L, Mesocyclops_edax_Ind_L, Copepodite_cyclopods_Ind_L, Copepodite_calanoids_Ind_L, Nauplii_Ind_L ## Code/software #### **Software: R** * **Name:** R (The R Project for Statistical Computing) * **Version Used:** R 4.3.1 * **License:** GNU General Public License * **Website:** [https://cran.r-project.org](https://cran.r-project.org)