Data from: Do experimental pH increases alter the structure and function of a lowland tropical stream?

Disturbances can alter the structure and function of ecosystems. In stream
ecosystems, changes in discharge and physicochemistry at short,
intermediate, and long recurrence intervals can affect food webs and
ecosystem processes. In this paper, we compare pH regimes in streams at La
Selva Biological Station, Costa Rica, where episodic acidification
frequency across the stream network varies widely due to buffering from
inputs of bicarbonate-rich inter-basin groundwater. To examine the effects
of acidification on ecosystem structure and function, we experimentally
increased the buffering capacity of a headwater stream reach, and compared
it to an unbuffered upstream reach. We compared these reaches to a
naturally buffered and unbuffered reaches of a second headwater stream. We
quantified ecosystem structural (macroinvertebrate assemblages on leaf
litter and coarse woody debris), and functional responses (leaf litter and
coarse woody debris decomposition rates, and growth rates of a focal
insect taxon (Diptera: Chironomidae)). Non-metric multidimensional scaling
and analysis of similarity revealed that macroinvertebrate assemblages
were relatively homogenous across the four study reaches, although the
naturally buffered reach was the most dissimilar. Ecosystem function, as
measured by chironomid growth rates, was greater in the naturally buffered
reach, while decomposition rates did not differ across the four reaches.
Our results indicate that biological assemblages are adapted to pH regimes
of frequently acidified stream reaches. Our experiment informs the effects
on structure and function at short time scales in streams that experience
moderate acidification, but larger magnitude acidification events in
response to hydroclimatic change, as projected under climate change
scenarios, may induce stronger responses in streams.