.main-navigation {
  @include row;
  border-bottom: $base-border;
  margin-bottom: $large-spacing;
  margin-top: $small-spacing;
}

.navigation-breadcrumbs {
  margin-bottom: $small-spacing;

  @include media(rem(600)) {
    float: left;
    margin-bottom: 0;
    padding-bottom: $base-spacing;
  }

  li {
    display: inline-block;

    &:after {
      @include size(6px 10px);
      background-image: image-url("breadcrumb-cheveron.svg");
      background-position: center center;
      background-repeat: no-repeat;
      content: "";
      display: inline-block;
      margin: 0 $small-spacing;
    }

    &:last-child:after {
      display: none;
    }
  }

  a {
    color: $base-font-color;
    font-weight: bold;

    &:hover {
      color: $action-color;
    }
  }
}

.main-navigation {
  @include row;
  border-bottom: $base-border;
  margin-bottom: $base-spacing;
  margin-top: $small-spacing;
}

.navigation-breadcrumbs {
  margin-bottom: $small-spacing;

  @include media(rem(600)) {
    float: left;
    margin-bottom: 0;
    padding-bottom: $base-spacing;
  }

  li {
    display: inline-block;

    &:after {
      @include size(6px 10px);
      background-image: image-url("breadcrumb-cheveron.svg");
      background-position: center center;
      background-repeat: no-repeat;
      content: "";
      display: inline-block;
      margin: 0 $small-spacing;
    }

    &:last-child:after {
      display: none;
    }
  }

  a {
    color: $base-font-color;
    font-weight: bold;

    &:hover {
      color: $action-color;
    }
  }
}

Reduce margin below main nav
[JRO] Reduce margin below main nav

This makes the vertical distance between the "start a new topic" title field and what's below, and above, the same.