Abstract

The Northern Highlands Lake District (NHLD) is one of the few regions in the world with periodic comprehensive water chemistry data from hundreds of lakes spanning almost a century. Birge and Juday directed the first comprehensive assessment of water chemistry in the NHLD, sampling more than 600 lakes in the 1920s and 30s. These surveys have been repeated by various agencies and we now have data from the 1920s (UW), 1960s (WDNR), 1970s (EPA), 1980s (EPA), 1990s (EPA), and 2000s (NTL). The 28 lakes sampled as part of the Regional Lake Survey have been sampled by at least four of these regional surveys including the 1920s Birge and Juday sampling efforts. These 28 lakes were selected to represent a gradient of landscape position and shoreline development, both of which are important factors influencing social and ecological dynamics of lakes in the NHLD. This long-term regional dataset will lead to a greater understanding of whether and how large-scale drivers such as climate change and variability, lakeshore residential development, introductions of invasive species, or forest management have altered regional water chemistry. The purpose of the macrophyte survey is to identify, and quantify the types of aquatic plants within the various 28 regional survey lakes. The macrophyte survey consists of sampling macrophyte plants using a metal rake attached to a 15ft pole at approximately 140 spatially resolved points on a lake that are spread out in a grid like fashion, equally spaced from each other. Sampling locations were chosen such that the maximum depth at which macrophytes were surveyed was equal to or less than 15ft of water. Macrophyte sampling occurs in the latter part of the summer (after July 10) to ensure that macrophytes have had adequate time to grow and our sampling efforts capture the typical summer macrophyte community in each lake. Macrophyte sampling in these 28 lakes is ongoing and will be repeated approximately once every six years.

Abstract

Macrophyte surveys were conducted on Sparkling Lake, Vilas County, Wisconsin in mid-July of the years 2001 to 2004 and 2007 to 2009. Eight sites were chosen that corresponded to trap survey sites for rusty crayfish and represented the range of macrophyte communities in the lake. At each site, we swam a transect perpendicular to shore from 0 to 4 m depths. A tape measure extended from shore to the 4 m depth contour, and buoys were placed at the 1, 2, 3, and 4 m depth contours. Quadrats were placed along each transect at 1 m intervals. We visually estimated the percent cover of each macrophyte species within a 0.24 meter squared quadrat. Transect: corresponds to trap survey site number. Quadrat: occur at 1 m intervals starting from shore (0) and going until you reach the 4 m depth contour (highest number). Substrate: substrate within the quadrat categorized as muck, sand, gravel, cobble, logs, leaves, or any combination of these. Abundance: percent cover of each species within the quadrat determined by visual estimation. The percent covers of all species within a quadrat do NOT necessarily add to 100. Depth Interval: depth interval that each quadrat was in. Quadrats between 0 and 1 m deep are in depth interval 1, those between 1 and 2 m deep are in depth interval 2, etc. Number of sites: 8 Sampling Frequency: annually during summer