DOI: 10.5061/dryad.nh6hn04
title: Data from: Organic matter loading by hippopotami causes subsidy overload resulting in downstream hypoxia and fish kills

description: Organic matter and nutrient loading into aquatic ecosystems affects
 ecosystem structure and function and can result in eutrophication and
 hypoxia. Hypoxia is usually attributed to anthropogenic pollution and is
 rarely documented in unpolluted systems, particularly in rivers. Here we
 show that organic matter loading from hippopotami causes the repeated
 occurrence of hypoxia in the Mara River, East Africa. We documented 49
 high flow events over three years that caused dissolved oxygen decreases,
 including 13 events resulting in hypoxia, and 9 fish kills over five
 years. Evidence from experiments and modeling demonstrates a strong
 mechanistic link between the flushing of hippo pools and decreased
 dissolved oxygen. This phenomenon may have been more widespread throughout
 Africa before hippo populations were severely reduced. Frequent hypoxia
 may be a natural part of tropical river ecosystem function, which directly
 challenges our notions of the reference state of rivers in the absence of
 human influence.
description: READMEREADME file describing
 the data contained within this repository.Raw_Discharge_and_DO_Data_Dec2012-March2015This file contains the raw dissolved oxygen and discharge data collected from the sonde at the Purungat Bridge between December 2012 and March 2015. The sonde initially recorded depth data with a pressure transducer. We also recorded changes in barometric pressure and then corrected the sonde depth values with the barometric pressure data then applied our rating curve to calculate discharge in m3/s (see Methods). Dissolved oxygen is provided in percent saturation and mg/L. Measurements were taken every 15 minutes. Please note, this is the raw data. Below a value of approximately 4 to 5 m3/s, you will notice dissolved oxygen starts to gradually drop over the course of several days. This is due to the location that our sonde is installed in the river. It becomes disconnected from the main channel as discharge falls somewhere between 4 to 5 m3/s and dissolved oxygen is more represented as a partially connected pool and not the main river channel.55_Flushing_FlowsThis file contains data on the 55 flushing flows identified from the Raw_Discharge_and_DO_Data_Dec2012-March2015.csv. This datasheet was created by examining the 55 flushing flows and recording information about discharge and dissolved oxygen during the flushing flows. Column titles are provided in row 1 and units are provided in row 2. In columns 1 and 2, flood origin was determined by examining other sources of hydrology data for the Upper Mara and Talek catchments.44_Flushing_Flows_Multiple_Linear_RegressionThis is a subset of data from the 55_Flushing_Flows.csv file. This is the data that was utilized to create the multiple linear regression of flushing flows in which the timing of previous flushing flow was known.Experimental_Streams_Hippo_Feces_AdditionThis file contains the data for plotting Fig 2b. This is data from an experiment where different concentrations of hippo feces were added to recirculating experimental streams and dissolved oxygen was logged in each stream every 5 minutes. This data has been cleaned up and error checked from the original raw data. Four columns: Minutes (Time since beginning of the experiment), variable (the specific treatment channel), value (dissolved oxygen in mg/L), and type (Hippo Feces).Experimental_Streams_HPW_AdditionThis file contains the data for plotting Fig 2c. This is data from an experiment where different concentrations of hipppo pool water (HPW) were added to recirculating experimental streams and dissolved oxygen was logged in each stream every 5 minutes. This data has been cleaned up and error checked from the original raw data. Four columns: Minutes (time since beginning of the experiment), variable (the specific treatment channel), value (dissolved oxygen in mg/L), and type (HPW).Robot_Boat_Hippo_Pool_Stratification_AmaniMaraThis file contains the conductivity measurements taken at different depths for the Amani Mara Hippo Pool. See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Robot_Boat_Hippo_Pool_Stratification_CrocThis file contains the conductivity measurements taken at different depths for the Croc Hippo Pool. See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Robot_Boat_Hippo_Pool_Stratification_EmartiThis file contains the conductivity measurements taken at different depths for the Emarti Pool. See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Robot_Boat_Hippo_Pool_Stratification_HPAThis file contains the conductivity measurements taken at different depths for the HPA Hippo Pool. See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Robot_Boat_Hippo_Pool_Stratification_MolibandThis file contains the conductivity measurements taken at different depths for the Moliband Pool. See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Robot_Boat_Hippo_Pool_Stratification_GPS_EmartiThis file contains the conductivity measurements taken at different depths for the Emarti Pool along with the GPS information (Latitude and Longitude in decimal degrees). See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Robot_Boat_Hippo_Pool_Stratification_GPS_AmaniMaraThis file contains the conductivity measurements taken at different depths for the Amani Mara Hippo Pool along with the GPS information (Latitude and Longitude in decimal degrees). See the Methods and Supplementary Information in the manuscript for more details about the location of the pool.Sediment_Fingeprinting_SourcesThis file contains the raw elemental data for the 4 different types of sources within the catchment (Upper Mara, Middle Mara, Talek, and Hippo). All elemental data is provided in ppm (parts per million).Sediment_Fingeprinting_Dec10-2013_SamplesThis file contains the raw elemental data for the time series of samples collected at the Purungat bridge beginning on December 10, 2013. All elemental data is provided in ppm (parts per million).Sediment_Fingeprinting_March14-2014_SamplesThis file contains the raw elemental data for the time series of samples collected at the Purungat bridge beginning on March 14, 2014. All elemental data is provided in ppm (parts per million).Sediment_Fingeprinting_Oct27-2012_SamplesThis file contains the raw elemental data for the time series of samples collected at the Purungat bridge beginning on October 27, 2012. All elemental data is provided in ppm (parts per million).