Fig 1.
Río San Juan basin in its entirety and Río San Juan from Lake Nicaragua downstream to the Caribbean Sea.
Fig 2.
Reach of Río San Juan from approximately River Km 83.3 to 84.3 (downstream of the outlet of Lake Nicaragua).
Massive cuts in steep slopes and large, eroding fill piles are visible, along with freshly deposited deltas of sediment built of road-derived sediment. The deep cut slopes and massive fill piles are subject not only to sheet erosion, but deep gully erosion and mass failures as inadequate stream culverts have blown out. Sediment is transported directly from eroding surfaces into the Río San Juan, some remaining as delta deposits. Sample sites S-3, S-4, and S-5 are identified in the photo. The boat visible in river (near center of photo) is about 7 m long. Oblique aerial view looking south by Kondolf, March 2015.
Fig 3.
Detail of sampled reach, showing river downstream of Lake Nicaragua outlet, areas of severe erosion due to disturbance from road construction, and locations of sample sites.
Table 1.
Land uses of sampling sites along the South and North Banks of the Río San Juan (Drainages unnamed except as indicated).
Fig 4.
Collecting benthic macroinvertebrate sample using D-net on freshly deposited delta sediments (site S-2).
Photo looking upstream, by Walls, March 2014.
Table 2.
Substrate and environmental characteristics of sampling sites on the Río San Juan.
Fig 5.
Periphyton biomass (chlorophyll a) on benthic substrate (cobbles and pebbles) in deltas along the south versus north banks of the Río San Juan, March-May 2014.
Values are logx+1 transformed.
Table 3.
Mean, Minimum and Maximum Chlorophyll a Values Sampled from South (S) and North (N)-bank Sites.
Fig 6.
Macroinvertebrate richness of south-bank versus north-bank tributary deltas of the Río San Juan, March-May 2014.
Table 4.
Macroinvertebrate Metrics Sampled from South (S) and North (N)-bank Tributary Delta Sites on the Río San Juan.
Fig 7.
Macroinvertebrate abundance of south-bank versus north-bank tributary deltas of the Río San Juan, March-May 2014.
Table 5.
ANCOVA P-values for Biological Metrics with Watershed Area, % of Catchment Forested and Bank (North and South Banks of Río San Juan, Nicaragua).
Fig 8.
Non-Metric Multidimensional Scaling (NMDS) of macroinvertebrate assemblages sampled at north-bank (circles) and south-bank (triangles) tributary deltas of the Río San Juan.
Vectors represent the substrate and environmental variables measured, fitted in the space of variation of macroinvertebrate composition. NMDS stress is 0.185.
Fig 9.
Location of CCT’s paired sampling sites on south-bank tributaries, upstream and downstream of the Rte 1856 crossing of the Río San Juan, showing also our sample sites for reference [46].